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	$87.97	10.142%	$96.8919	$96.89	$96.90	$96.90
Purchase #2	$77.41	5.822%	$81.9168	$81.92	$81.90	$81.90
Purchase #3	$193.68	10.862%	$214.7175	$214.72	$214.70	$214.70
Purchase #4	$156.72	13.736%	$178.2471	$178.25	$178.25	$178.20
Purchase #5	$189.91	3.658%	$196.8569	$196.86	$196.85	$196.90
Purchase #6	$187.43	4.793%	$196.4135	$196.41	$196.40	$196.40
Purchase #7	$241.61	3.376%	$249.7668	$249.77	$249.75	$249.80
7 purchase totals =	$1,134.73		$1,214.8105	$1,214.82	$1,214.75	$1,214.80