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	$106.28	3.665%	$110.1752	$110.18	$110.20	$110.20
Purchase #2	$133.30	13.617%	$151.4515	$151.45	$151.45	$151.50
Purchase #3	$189.73	10.108%	$208.9079	$208.91	$208.90	$208.90
Purchase #4	$92.78	4.288%	$96.7584	$96.76	$96.75	$96.80
Purchase #5	$54.44	10.116%	$59.9472	$59.95	$59.95	$59.90
Purchase #6	$183.39	7.115%	$196.4382	$196.44	$196.45	$196.40
Purchase #7	$54.41	9.784%	$59.7335	$59.73	$59.75	$59.70
7 purchase totals =	$814.33		$883.4119	$883.42	$883.45	$883.40