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	$53.43	10.210%	$58.8852	$58.89	$58.90	$58.90
Purchase #2	$94.32	4.580%	$98.6399	$98.64	$98.65	$98.60
Purchase #3	$55.94	10.655%	$61.9004	$61.90	$61.90	$61.90
Purchase #4	$96.32	3.149%	$99.3531	$99.35	$99.35	$99.40
Purchase #5	$147.94	8.770%	$160.9143	$160.91	$160.90	$160.90
Purchase #6	$196.68	7.560%	$211.549	$211.55	$211.55	$211.50
Purchase #7	$59.61	10.681%	$65.9769	$65.98	$66.00	$66.00
7 purchase totals =	$704.24		$757.2188	$757.22	$757.25	$757.20