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	$158.31	12.571%	$178.2112	$178.21	$178.20	$178.20
Purchase #2	$86.93	7.516%	$93.4637	$93.46	$93.45	$93.50
Purchase #3	$123.65	5.415%	$130.3456	$130.35	$130.35	$130.30
Purchase #4	$213.63	12.371%	$240.0582	$240.06	$240.05	$240.10
Purchase #5	$198.54	4.819%	$208.1076	$208.11	$208.10	$208.10
Purchase #6	$142.55	6.339%	$151.5862	$151.59	$151.60	$151.60
Purchase #7	$53.94	11.332%	$60.0525	$60.05	$60.05	$60.10
7 purchase totals =	$977.55		$1,061.8250	$1,061.83	$1,061.80	$1,061.90