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	$210.30	6.160%	$223.2545	$223.25	$223.25	$223.30
Purchase #2	$138.26	12.748%	$155.8854	$155.89	$155.90	$155.90
Purchase #3	$46.49	10.346%	$51.2999	$51.30	$51.30	$51.30
Purchase #4	$31.59	6.450%	$33.6276	$33.63	$33.65	$33.60
Purchase #5	$177.88	7.320%	$190.9008	$190.90	$190.90	$190.90
Purchase #6	$238.96	11.146%	$265.5945	$265.59	$265.60	$265.60
Purchase #7	$242.27	9.251%	$264.6824	$264.68	$264.70	$264.70
7 purchase totals =	$1,085.75		$1,185.2451	$1,185.24	$1,185.30	$1,185.30