Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$125.37	13.478%	$142.2674	$142.27	$142.25	$142.30
Purchase #2	$136.93	9.643%	$150.1342	$150.13	$150.15	$150.10
Purchase #3	$106.36	7.122%	$113.935	$113.94	$113.95	$113.90
Purchase #4	$228.70	13.129%	$258.726	$258.73	$258.75	$258.70
Purchase #5	$242.91	10.872%	$269.3192	$269.32	$269.30	$269.30
Purchase #6	$159.43	13.558%	$181.0455	$181.05	$181.05	$181.00
Purchase #7	$98.46	13.450%	$111.7029	$111.70	$111.70	$111.70
7 purchase totals =	$1,098.16		$1,227.1302	$1,227.14	$1,227.15	$1,227.00