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	$198.55	7.151%	$212.7483	$212.75	$212.75	$212.70
Purchase #2	$61.48	6.642%	$65.5635	$65.56	$65.55	$65.60
Purchase #3	$196.66	6.489%	$209.4213	$209.42	$209.40	$209.40
Purchase #4	$185.25	4.150%	$192.9379	$192.94	$192.95	$192.90
Purchase #5	$135.60	13.793%	$154.3033	$154.30	$154.30	$154.30
Purchase #6	$96.39	3.235%	$99.5082	$99.51	$99.50	$99.50
Purchase #7	$126.80	11.446%	$141.3135	$141.31	$141.30	$141.30
7 purchase totals =	$1,000.73		$1,075.7960	$1,075.79	$1,075.75	$1,075.70