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	$169.76	12.639%	$191.216	$191.22	$191.20	$191.20
Purchase #2	$50.63	5.783%	$53.5579	$53.56	$53.55	$53.60
Purchase #3	$245.80	12.652%	$276.8986	$276.90	$276.90	$276.90
Purchase #4	$155.42	4.695%	$162.717	$162.72	$162.70	$162.70
Purchase #5	$219.73	10.306%	$242.3754	$242.38	$242.40	$242.40
Purchase #6	$97.56	6.815%	$104.2087	$104.21	$104.20	$104.20
Purchase #7	$227.99	12.413%	$256.2904	$256.29	$256.30	$256.30
7 purchase totals =	$1,166.89		$1,287.2640	$1,287.28	$1,287.25	$1,287.30