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	$111.31	3.726%	$115.4574	$115.46	$115.45	$115.50
Purchase #2	$194.57	8.635%	$211.3711	$211.37	$211.35	$211.40
Purchase #3	$77.38	6.610%	$82.4948	$82.49	$82.50	$82.50
Purchase #4	$9.93	5.819%	$10.5078	$10.51	$10.50	$10.50
Purchase #5	$83.99	11.359%	$93.5304	$93.53	$93.55	$93.50
Purchase #6	$162.56	6.296%	$172.7948	$172.79	$172.80	$172.80
Purchase #7	$98.31	6.816%	$105.0108	$105.01	$105.00	$105.00
7 purchase totals =	$738.05		$791.1671	$791.16	$791.15	$791.20