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	$65.78	10.115%	$72.4336	$72.43	$72.45	$72.40
Purchase #2	$81.45	4.560%	$85.1641	$85.16	$85.15	$85.20
Purchase #3	$92.33	11.740%	$103.1695	$103.17	$103.15	$103.20
Purchase #4	$94.40	9.566%	$103.4303	$103.43	$103.45	$103.40
Purchase #5	$192.69	7.120%	$206.4095	$206.41	$206.40	$206.40
Purchase #6	$249.78	11.330%	$278.0801	$278.08	$278.10	$278.10
Purchase #7	$199.82	11.756%	$223.3108	$223.31	$223.30	$223.30
7 purchase totals =	$976.25		$1,071.9979	$1,071.99	$1,072.00	$1,072.00