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	$77.82	4.464%	$81.2939	$81.29	$81.30	$81.30
Purchase #2	$24.25	13.689%	$27.5696	$27.57	$27.55	$27.60
Purchase #3	$234.72	3.581%	$243.1253	$243.13	$243.15	$243.10
Purchase #4	$65.29	11.541%	$72.8251	$72.83	$72.85	$72.80
Purchase #5	$213.95	4.330%	$223.214	$223.21	$223.20	$223.20
Purchase #6	$33.63	10.810%	$37.2654	$37.27	$37.25	$37.30
Purchase #7	$241.99	10.774%	$268.062	$268.06	$268.05	$268.10
7 purchase totals =	$891.65		$953.3553	$953.36	$953.35	$953.40