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	$82.89	7.334%	$88.9692	$88.97	$88.95	$89.00
Purchase #2	$55.41	7.673%	$59.6616	$59.66	$59.65	$59.70
Purchase #3	$90.35	6.316%	$96.0565	$96.06	$96.05	$96.10
Purchase #4	$197.27	9.114%	$215.2492	$215.25	$215.25	$215.20
Purchase #5	$50.62	4.613%	$52.9551	$52.96	$52.95	$53.00
Purchase #6	$98.88	5.155%	$103.9773	$103.98	$104.00	$104.00
Purchase #7	$53.45	13.608%	$60.7235	$60.72	$60.70	$60.70
7 purchase totals =	$628.87		$677.5924	$677.60	$677.55	$677.70