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	$177.88	7.818%	$191.7867	$191.79	$191.80	$191.80
Purchase #2	$113.74	4.499%	$118.8572	$118.86	$118.85	$118.90
Purchase #3	$10.41	12.205%	$11.6805	$11.68	$11.70	$11.70
Purchase #4	$247.76	3.617%	$256.7215	$256.72	$256.70	$256.70
Purchase #5	$133.64	9.274%	$146.0338	$146.03	$146.05	$146.00
Purchase #6	$109.79	5.809%	$116.1677	$116.17	$116.15	$116.20
Purchase #7	$233.60	11.168%	$259.6884	$259.69	$259.70	$259.70
7 purchase totals =	$1,026.82		$1,100.9358	$1,100.94	$1,100.95	$1,101.00