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	$46.63	11.762%	$52.1146	$52.11	$52.10	$52.10
Purchase #2	$246.61	11.499%	$274.9677	$274.97	$274.95	$275.00
Purchase #3	$85.31	4.821%	$89.4228	$89.42	$89.40	$89.40
Purchase #4	$160.92	10.713%	$178.1594	$178.16	$178.15	$178.20
Purchase #5	$158.54	13.573%	$180.0586	$180.06	$180.05	$180.10
Purchase #6	$138.81	4.191%	$144.6275	$144.63	$144.65	$144.60
Purchase #7	$153.37	6.138%	$162.7839	$162.78	$162.80	$162.80
7 purchase totals =	$990.19		$1,082.1345	$1,082.13	$1,082.10	$1,082.20