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	$191.73	10.107%	$211.1082	$211.11	$211.10	$211.10
Purchase #2	$112.85	4.814%	$118.2826	$118.28	$118.30	$118.30
Purchase #3	$85.90	6.391%	$91.3899	$91.39	$91.40	$91.40
Purchase #4	$232.43	3.592%	$240.7789	$240.78	$240.80	$240.80
Purchase #5	$28.69	13.816%	$32.6538	$32.65	$32.65	$32.70
Purchase #6	$87.87	4.276%	$91.6273	$91.63	$91.65	$91.60
Purchase #7	$193.50	12.492%	$217.672	$217.67	$217.65	$217.70
7 purchase totals =	$932.97		$1,003.5127	$1,003.51	$1,003.55	$1,003.60