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	$96.37	3.556%	$99.7969	$99.80	$99.80	$99.80
Purchase #2	$19.32	6.820%	$20.6376	$20.64	$20.65	$20.60
Purchase #3	$21.94	8.109%	$23.7191	$23.72	$23.70	$23.70
Purchase #4	$100.89	11.649%	$112.6427	$112.64	$112.65	$112.60
Purchase #5	$235.41	8.165%	$254.6312	$254.63	$254.65	$254.60
Purchase #6	$130.51	11.633%	$145.6922	$145.69	$145.70	$145.70
Purchase #7	$55.96	3.472%	$57.9029	$57.90	$57.90	$57.90
7 purchase totals =	$660.40		$715.0226	$715.02	$715.05	$714.90