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	$169.45	9.532%	$185.602	$185.60	$185.60	$185.60
Purchase #2	$186.46	13.222%	$211.1137	$211.11	$211.10	$211.10
Purchase #3	$41.72	13.329%	$47.2809	$47.28	$47.30	$47.30
Purchase #4	$53.25	7.623%	$57.3092	$57.31	$57.30	$57.30
Purchase #5	$13.68	5.152%	$14.3848	$14.38	$14.40	$14.40
Purchase #6	$24.69	7.687%	$26.5879	$26.59	$26.60	$26.60
Purchase #7	$115.60	8.511%	$125.4387	$125.44	$125.45	$125.40
7 purchase totals =	$604.85		$667.7172	$667.71	$667.75	$667.70