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	$235.35	4.345%	$245.576	$245.58	$245.60	$245.60
Purchase #2	$173.45	5.267%	$182.5856	$182.59	$182.60	$182.60
Purchase #3	$244.59	7.242%	$262.3032	$262.30	$262.30	$262.30
Purchase #4	$143.89	11.641%	$160.6402	$160.64	$160.65	$160.60
Purchase #5	$203.99	3.588%	$211.3092	$211.31	$211.30	$211.30
Purchase #6	$162.84	4.588%	$170.3111	$170.31	$170.30	$170.30
Purchase #7	$64.34	4.744%	$67.3923	$67.39	$67.40	$67.40
7 purchase totals =	$1,228.45		$1,300.1176	$1,300.12	$1,300.15	$1,300.10