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	$80.46	10.347%	$88.7852	$88.79	$88.80	$88.80
Purchase #2	$68.77	4.501%	$71.8653	$71.87	$71.85	$71.90
Purchase #3	$65.36	11.638%	$72.9666	$72.97	$72.95	$73.00
Purchase #4	$64.69	10.192%	$71.2832	$71.28	$71.30	$71.30
Purchase #5	$155.55	9.540%	$170.3895	$170.39	$170.40	$170.40
Purchase #6	$90.55	7.429%	$97.277	$97.28	$97.30	$97.30
Purchase #7	$178.45	7.211%	$191.318	$191.32	$191.30	$191.30
7 purchase totals =	$703.83		$763.8848	$763.90	$763.90	$764.00