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	$174.27	7.664%	$187.6261	$187.63	$187.65	$187.60
Purchase #2	$191.90	4.416%	$200.3743	$200.37	$200.35	$200.40
Purchase #3	$18.92	11.504%	$21.0966	$21.10	$21.10	$21.10
Purchase #4	$238.28	10.426%	$263.1231	$263.12	$263.10	$263.10
Purchase #5	$250.60	12.357%	$281.5666	$281.57	$281.55	$281.60
Purchase #6	$130.51	4.551%	$136.4495	$136.45	$136.45	$136.40
Purchase #7	$89.88	10.602%	$99.4091	$99.41	$99.40	$99.40
7 purchase totals =	$1,094.36		$1,189.6453	$1,189.65	$1,189.60	$1,189.60