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	$73.50	9.178%	$80.2458	$80.25	$80.25	$80.20
Purchase #2	$147.84	3.679%	$153.279	$153.28	$153.30	$153.30
Purchase #3	$181.26	5.114%	$190.5296	$190.53	$190.55	$190.50
Purchase #4	$241.64	6.104%	$256.3897	$256.39	$256.40	$256.40
Purchase #5	$85.99	5.731%	$90.9181	$90.92	$90.90	$90.90
Purchase #6	$111.35	11.692%	$124.369	$124.37	$124.35	$124.40
Purchase #7	$69.73	3.122%	$71.907	$71.91	$71.90	$71.90
7 purchase totals =	$911.31		$967.6382	$967.65	$967.65	$967.60