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	$39.49	5.188%	$41.5387	$41.54	$41.55	$41.50
Purchase #2	$85.57	5.234%	$90.0487	$90.05	$90.05	$90.00
Purchase #3	$75.36	3.385%	$77.9109	$77.91	$77.90	$77.90
Purchase #4	$131.54	5.303%	$138.5156	$138.52	$138.50	$138.50
Purchase #5	$80.33	9.730%	$88.1461	$88.15	$88.15	$88.10
Purchase #6	$140.26	4.653%	$146.7863	$146.79	$146.80	$146.80
Purchase #7	$179.84	9.188%	$196.3637	$196.36	$196.35	$196.40
7 purchase totals =	$732.39		$779.3100	$779.32	$779.30	$779.20