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	$80.88	10.849%	$89.6547	$89.65	$89.65	$89.70
Purchase #2	$78.70	8.507%	$85.395	$85.40	$85.40	$85.40
Purchase #3	$133.75	12.512%	$150.4848	$150.48	$150.50	$150.50
Purchase #4	$82.73	11.617%	$92.3407	$92.34	$92.35	$92.30
Purchase #5	$175.25	9.632%	$192.1301	$192.13	$192.15	$192.10
Purchase #6	$144.75	9.858%	$159.0195	$159.02	$159.00	$159.00
Purchase #7	$249.80	6.417%	$265.8297	$265.83	$265.85	$265.80
7 purchase totals =	$945.86		$1,034.8545	$1,034.85	$1,034.90	$1,034.80