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	$169.56	9.804%	$186.1837	$186.18	$186.20	$186.20
Purchase #2	$6.80	7.147%	$7.286	$7.29	$7.30	$7.30
Purchase #3	$109.82	9.820%	$120.6043	$120.60	$120.60	$120.60
Purchase #4	$245.75	3.403%	$254.1129	$254.11	$254.10	$254.10
Purchase #5	$148.79	9.197%	$162.4742	$162.47	$162.45	$162.50
Purchase #6	$151.47	4.267%	$157.9332	$157.93	$157.95	$157.90
Purchase #7	$188.62	4.358%	$196.8401	$196.84	$196.85	$196.80
7 purchase totals =	$1,020.81		$1,085.4344	$1,085.42	$1,085.45	$1,085.40