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	$60.84	10.539%	$67.2519	$67.25	$67.25	$67.30
Purchase #2	$229.81	6.842%	$245.5336	$245.53	$245.55	$245.50
Purchase #3	$40.28	12.393%	$45.2719	$45.27	$45.25	$45.30
Purchase #4	$75.76	10.441%	$83.6701	$83.67	$83.65	$83.70
Purchase #5	$142.38	3.590%	$147.4914	$147.49	$147.50	$147.50
Purchase #6	$141.46	6.338%	$150.4257	$150.43	$150.45	$150.40
Purchase #7	$171.33	4.139%	$178.4213	$178.42	$178.40	$178.40
7 purchase totals =	$861.86		$918.0659	$918.06	$918.05	$918.10