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	$54.75	9.361%	$59.8751	$59.88	$59.90	$59.90
Purchase #2	$78.51	9.139%	$85.685	$85.69	$85.70	$85.70
Purchase #3	$88.49	11.582%	$98.7389	$98.74	$98.75	$98.70
Purchase #4	$228.85	6.543%	$243.8237	$243.82	$243.80	$243.80
Purchase #5	$140.70	13.845%	$160.1799	$160.18	$160.20	$160.20
Purchase #6	$235.53	7.801%	$253.9037	$253.90	$253.90	$253.90
Purchase #7	$54.82	9.296%	$59.9161	$59.92	$59.90	$59.90
7 purchase totals =	$881.65		$962.1224	$962.13	$962.15	$962.10