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	$117.52	5.121%	$123.5382	$123.54	$123.55	$123.50
Purchase #2	$158.95	4.415%	$165.9676	$165.97	$165.95	$166.00
Purchase #3	$115.96	4.253%	$120.8918	$120.89	$120.90	$120.90
Purchase #4	$99.87	4.495%	$104.3592	$104.36	$104.35	$104.40
Purchase #5	$206.44	9.552%	$226.1591	$226.16	$226.15	$226.20
Purchase #6	$61.41	5.667%	$64.8901	$64.89	$64.90	$64.90
Purchase #7	$162.29	6.175%	$172.3114	$172.31	$172.30	$172.30
7 purchase totals =	$922.44		$978.1174	$978.12	$978.10	$978.20