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	$149.49	4.175%	$155.7312	$155.73	$155.75	$155.70
Purchase #2	$152.71	9.222%	$166.7929	$166.79	$166.80	$166.80
Purchase #3	$233.28	9.321%	$255.024	$255.02	$255.00	$255.00
Purchase #4	$48.83	8.465%	$52.9635	$52.96	$52.95	$53.00
Purchase #5	$141.34	6.518%	$150.5525	$150.55	$150.55	$150.60
Purchase #6	$36.56	3.215%	$37.7354	$37.74	$37.75	$37.70
Purchase #7	$178.79	7.107%	$191.4966	$191.50	$191.50	$191.50
7 purchase totals =	$941.00		$1,010.2961	$1,010.29	$1,010.30	$1,010.30