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	$42.59	3.413%	$44.0436	$44.04	$44.05	$44.00
Purchase #2	$166.31	9.179%	$181.5756	$181.58	$181.60	$181.60
Purchase #3	$124.51	4.542%	$130.1652	$130.17	$130.15	$130.20
Purchase #4	$140.65	7.469%	$151.1551	$151.16	$151.15	$151.20
Purchase #5	$178.82	3.649%	$185.3451	$185.35	$185.35	$185.30
Purchase #6	$98.74	4.755%	$103.4351	$103.44	$103.45	$103.40
Purchase #7	$234.58	12.552%	$264.0245	$264.02	$264.00	$264.00
7 purchase totals =	$986.20		$1,059.7442	$1,059.76	$1,059.75	$1,059.70