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	$189.33	3.230%	$195.4454	$195.45	$195.45	$195.40
Purchase #2	$54.41	9.225%	$59.4293	$59.43	$59.45	$59.40
Purchase #3	$182.63	13.773%	$207.7836	$207.78	$207.80	$207.80
Purchase #4	$54.44	9.459%	$59.5895	$59.59	$59.60	$59.60
Purchase #5	$47.98	7.349%	$51.5061	$51.51	$51.50	$51.50
Purchase #6	$12.40	8.569%	$13.4626	$13.46	$13.45	$13.50
Purchase #7	$89.32	8.127%	$96.579	$96.58	$96.60	$96.60
7 purchase totals =	$630.51		$683.7955	$683.80	$683.85	$683.80