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	$142.31	6.424%	$151.452	$151.45	$151.45	$151.50
Purchase #2	$124.72	7.808%	$134.4581	$134.46	$134.45	$134.50
Purchase #3	$114.70	10.192%	$126.3902	$126.39	$126.40	$126.40
Purchase #4	$213.37	12.817%	$240.7176	$240.72	$240.70	$240.70
Purchase #5	$130.91	10.731%	$144.958	$144.96	$144.95	$145.00
Purchase #6	$103.64	7.415%	$111.3249	$111.32	$111.30	$111.30
Purchase #7	$121.80	13.132%	$137.7948	$137.79	$137.80	$137.80
7 purchase totals =	$951.45		$1,047.0956	$1,047.09	$1,047.05	$1,047.20