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	$147.72	3.838%	$153.3895	$153.39	$153.40	$153.40
Purchase #2	$59.54	4.518%	$62.23	$62.23	$62.25	$62.20
Purchase #3	$112.85	11.403%	$125.7183	$125.72	$125.70	$125.70
Purchase #4	$198.68	12.280%	$223.0779	$223.08	$223.10	$223.10
Purchase #5	$165.49	13.352%	$187.5862	$187.59	$187.60	$187.60
Purchase #6	$75.43	13.736%	$85.7911	$85.79	$85.80	$85.80
Purchase #7	$89.90	3.329%	$92.8928	$92.89	$92.90	$92.90
7 purchase totals =	$849.61		$930.6858	$930.69	$930.75	$930.70