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	$204.48	13.446%	$231.9744	$231.97	$231.95	$232.00
Purchase #2	$90.76	11.795%	$101.4651	$101.47	$101.45	$101.50
Purchase #3	$62.87	13.356%	$71.2669	$71.27	$71.25	$71.30
Purchase #4	$82.71	3.417%	$85.5362	$85.54	$85.55	$85.50
Purchase #5	$237.90	4.833%	$249.3977	$249.40	$249.40	$249.40
Purchase #6	$33.51	11.256%	$37.2819	$37.28	$37.30	$37.30
Purchase #7	$69.43	13.764%	$78.9863	$78.99	$79.00	$79.00
7 purchase totals =	$781.66		$855.9085	$855.92	$855.90	$856.00