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	$109.54	4.373%	$114.3302	$114.33	$114.35	$114.30
Purchase #2	$99.26	12.765%	$111.9305	$111.93	$111.95	$111.90
Purchase #3	$40.40	3.244%	$41.7106	$41.71	$41.70	$41.70
Purchase #4	$42.73	9.316%	$46.7107	$46.71	$46.70	$46.70
Purchase #5	$44.73	9.440%	$48.9525	$48.95	$48.95	$49.00
Purchase #6	$66.72	7.747%	$71.8888	$71.89	$71.90	$71.90
Purchase #7	$25.95	3.520%	$26.8634	$26.86	$26.85	$26.90
7 purchase totals =	$429.33		$462.3867	$462.38	$462.40	$462.40