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	$175.25	7.738%	$188.8108	$188.81	$188.80	$188.80
Purchase #2	$172.50	7.336%	$185.1546	$185.15	$185.15	$185.20
Purchase #3	$195.55	13.190%	$221.343	$221.34	$221.35	$221.30
Purchase #4	$57.28	9.542%	$62.7457	$62.75	$62.75	$62.70
Purchase #5	$73.64	9.244%	$80.4473	$80.45	$80.45	$80.40
Purchase #6	$175.25	9.291%	$191.5325	$191.53	$191.55	$191.50
Purchase #7	$135.86	5.458%	$143.2752	$143.28	$143.30	$143.30
7 purchase totals =	$985.33		$1,073.3091	$1,073.31	$1,073.35	$1,073.20