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	$130.39	8.543%	$141.5292	$141.53	$141.55	$141.50
Purchase #2	$22.51	11.443%	$25.0858	$25.09	$25.10	$25.10
Purchase #3	$131.64	9.750%	$144.4749	$144.47	$144.45	$144.50
Purchase #4	$77.76	10.464%	$85.8968	$85.90	$85.90	$85.90
Purchase #5	$166.76	7.527%	$179.312	$179.31	$179.30	$179.30
Purchase #6	$245.38	5.729%	$259.4378	$259.44	$259.45	$259.40
Purchase #7	$173.98	6.459%	$185.2174	$185.22	$185.20	$185.20
7 purchase totals =	$948.42		$1,020.9539	$1,020.96	$1,020.95	$1,020.90