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	$31.47	5.259%	$33.125	$33.13	$33.15	$33.10
Purchase #2	$53.88	7.213%	$57.7664	$57.77	$57.75	$57.80
Purchase #3	$218.70	4.400%	$228.3228	$228.32	$228.30	$228.30
Purchase #4	$72.86	13.265%	$82.5249	$82.52	$82.50	$82.50
Purchase #5	$239.32	4.659%	$250.4699	$250.47	$250.45	$250.50
Purchase #6	$240.92	5.845%	$255.0018	$255.00	$255.00	$255.00
Purchase #7	$154.43	12.742%	$174.1075	$174.11	$174.10	$174.10
7 purchase totals =	$1,011.58		$1,081.3183	$1,081.32	$1,081.25	$1,081.30