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	$57.26	4.502%	$59.8378	$59.84	$59.85	$59.80
Purchase #2	$27.60	9.251%	$30.1533	$30.15	$30.15	$30.20
Purchase #3	$78.37	9.802%	$86.0518	$86.05	$86.05	$86.10
Purchase #4	$184.94	6.335%	$196.6559	$196.66	$196.65	$196.70
Purchase #5	$26.51	4.139%	$27.6072	$27.61	$27.60	$27.60
Purchase #6	$206.83	8.146%	$223.6784	$223.68	$223.70	$223.70
Purchase #7	$41.40	9.305%	$45.2523	$45.25	$45.25	$45.30
7 purchase totals =	$622.91		$669.2367	$669.24	$669.25	$669.40