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	$43.63	5.102%	$45.856	$45.86	$45.85	$45.90
Purchase #2	$146.40	13.851%	$166.6779	$166.68	$166.70	$166.70
Purchase #3	$62.93	11.782%	$70.3444	$70.34	$70.35	$70.30
Purchase #4	$64.71	4.577%	$67.6718	$67.67	$67.65	$67.70
Purchase #5	$175.68	5.435%	$185.2282	$185.23	$185.25	$185.20
Purchase #6	$132.47	11.215%	$147.3265	$147.33	$147.35	$147.30
Purchase #7	$99.47	5.675%	$105.1149	$105.11	$105.10	$105.10
7 purchase totals =	$725.29		$788.2197	$788.22	$788.25	$788.20