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	$86.64	9.221%	$94.6291	$94.63	$94.65	$94.60
Purchase #2	$125.34	13.182%	$141.8623	$141.86	$141.85	$141.90
Purchase #3	$215.68	3.434%	$223.0865	$223.09	$223.10	$223.10
Purchase #4	$10.96	11.577%	$12.2288	$12.23	$12.25	$12.20
Purchase #5	$152.60	12.320%	$171.4003	$171.40	$171.40	$171.40
Purchase #6	$45.98	13.675%	$52.2678	$52.27	$52.25	$52.30
Purchase #7	$182.76	6.502%	$194.6431	$194.64	$194.65	$194.60
7 purchase totals =	$819.96		$890.1179	$890.12	$890.15	$890.10