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	$196.29	11.457%	$218.7789	$218.78	$218.80	$218.80
Purchase #2	$26.51	6.643%	$28.2711	$28.27	$28.25	$28.30
Purchase #3	$179.35	11.426%	$199.8425	$199.84	$199.85	$199.80
Purchase #4	$38.98	3.415%	$40.3112	$40.31	$40.30	$40.30
Purchase #5	$228.41	11.702%	$255.1385	$255.14	$255.15	$255.10
Purchase #6	$179.45	6.502%	$191.1178	$191.12	$191.10	$191.10
Purchase #7	$225.42	12.208%	$252.9393	$252.94	$252.95	$252.90
7 purchase totals =	$1,074.41		$1,186.3993	$1,186.40	$1,186.40	$1,186.30