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	$178.29	5.274%	$187.693	$187.69	$187.70	$187.70
Purchase #2	$72.62	7.588%	$78.1304	$78.13	$78.15	$78.10
Purchase #3	$223.92	12.486%	$251.8787	$251.88	$251.90	$251.90
Purchase #4	$58.47	6.123%	$62.0501	$62.05	$62.05	$62.10
Purchase #5	$30.55	3.180%	$31.5215	$31.52	$31.50	$31.50
Purchase #6	$114.42	3.528%	$118.4567	$118.46	$118.45	$118.50
Purchase #7	$159.56	4.806%	$167.2285	$167.23	$167.25	$167.20
7 purchase totals =	$837.83		$896.9589	$896.96	$897.00	$897.00