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	$49.97	6.145%	$53.0407	$53.04	$53.05	$53.00
Purchase #2	$135.87	9.159%	$148.3143	$148.31	$148.30	$148.30
Purchase #3	$197.36	12.665%	$222.3556	$222.36	$222.35	$222.40
Purchase #4	$77.87	3.711%	$80.7598	$80.76	$80.75	$80.80
Purchase #5	$195.43	6.821%	$208.7603	$208.76	$208.75	$208.80
Purchase #6	$130.51	10.656%	$144.4171	$144.42	$144.40	$144.40
Purchase #7	$166.50	7.655%	$179.2456	$179.25	$179.25	$179.20
7 purchase totals =	$953.51		$1,036.8934	$1,036.90	$1,036.85	$1,036.90