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	$231.74	10.143%	$255.2454	$255.25	$255.25	$255.20
Purchase #2	$103.88	6.223%	$110.3445	$110.34	$110.35	$110.30
Purchase #3	$75.31	5.265%	$79.2751	$79.28	$79.30	$79.30
Purchase #4	$233.58	9.354%	$255.4291	$255.43	$255.45	$255.40
Purchase #5	$212.65	7.718%	$229.0623	$229.06	$229.05	$229.10
Purchase #6	$70.33	11.719%	$78.572	$78.57	$78.55	$78.60
Purchase #7	$104.28	6.817%	$111.3888	$111.39	$111.40	$111.40
7 purchase totals =	$1,031.77		$1,119.3172	$1,119.32	$1,119.35	$1,119.30