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	$193.82	9.784%	$212.7833	$212.78	$212.80	$212.80
Purchase #2	$107.40	3.153%	$110.7863	$110.79	$110.80	$110.80
Purchase #3	$53.37	11.769%	$59.6511	$59.65	$59.65	$59.70
Purchase #4	$205.36	4.606%	$214.8189	$214.82	$214.80	$214.80
Purchase #5	$188.55	11.119%	$209.5149	$209.51	$209.50	$209.50
Purchase #6	$90.41	9.839%	$99.3054	$99.31	$99.30	$99.30
Purchase #7	$143.58	5.638%	$151.675	$151.68	$151.70	$151.70
7 purchase totals =	$982.49		$1,058.5349	$1,058.54	$1,058.55	$1,058.60