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	$11.32	6.430%	$12.0479	$12.05	$12.05	$12.00
Purchase #2	$151.31	10.132%	$166.6407	$166.64	$166.65	$166.60
Purchase #3	$57.40	3.533%	$59.4279	$59.43	$59.45	$59.40
Purchase #4	$159.31	7.671%	$171.5307	$171.53	$171.55	$171.50
Purchase #5	$128.79	10.462%	$142.264	$142.26	$142.25	$142.30
Purchase #6	$12.97	8.839%	$14.1164	$14.12	$14.10	$14.10
Purchase #7	$104.97	7.427%	$112.7661	$112.77	$112.75	$112.80
7 purchase totals =	$626.07		$678.7937	$678.80	$678.80	$678.70