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	$232.40	4.872%	$243.7225	$243.72	$243.70	$243.70
Purchase #2	$186.27	6.374%	$198.1428	$198.14	$198.15	$198.10
Purchase #3	$94.65	6.425%	$100.7313	$100.73	$100.75	$100.70
Purchase #4	$168.67	13.437%	$191.3342	$191.33	$191.35	$191.30
Purchase #5	$215.52	8.360%	$233.5375	$233.54	$233.55	$233.50
Purchase #6	$151.97	4.146%	$158.2707	$158.27	$158.25	$158.30
Purchase #7	$144.28	11.319%	$160.6111	$160.61	$160.60	$160.60
7 purchase totals =	$1,193.76		$1,286.3501	$1,286.34	$1,286.35	$1,286.20