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	$193.92	3.279%	$200.2786	$200.28	$200.30	$200.30
Purchase #2	$209.95	6.376%	$223.3364	$223.34	$223.35	$223.30
Purchase #3	$77.67	11.792%	$86.8288	$86.83	$86.85	$86.80
Purchase #4	$96.50	7.656%	$103.888	$103.89	$103.90	$103.90
Purchase #5	$180.57	9.273%	$197.3143	$197.31	$197.30	$197.30
Purchase #6	$167.64	6.806%	$179.0496	$179.05	$179.05	$179.00
Purchase #7	$155.40	12.718%	$175.1638	$175.16	$175.15	$175.20
7 purchase totals =	$1,081.65		$1,165.8595	$1,165.86	$1,165.90	$1,165.80