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	$175.82	3.342%	$181.6959	$181.70	$181.70	$181.70
Purchase #2	$81.31	12.568%	$91.529	$91.53	$91.55	$91.50
Purchase #3	$232.62	5.502%	$245.4188	$245.42	$245.40	$245.40
Purchase #4	$158.47	3.684%	$164.308	$164.31	$164.30	$164.30
Purchase #5	$86.52	5.548%	$91.3201	$91.32	$91.30	$91.30
Purchase #6	$243.86	6.269%	$259.1476	$259.15	$259.15	$259.10
Purchase #7	$182.49	3.478%	$188.837	$188.84	$188.85	$188.80
7 purchase totals =	$1,161.09		$1,222.2564	$1,222.27	$1,222.25	$1,222.10