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	$78.73	8.407%	$85.3488	$85.35	$85.35	$85.30
Purchase #2	$223.39	11.431%	$248.9257	$248.93	$248.95	$248.90
Purchase #3	$83.29	6.772%	$88.9304	$88.93	$88.95	$88.90
Purchase #4	$178.82	6.566%	$190.5613	$190.56	$190.55	$190.60
Purchase #5	$131.36	3.847%	$136.4134	$136.41	$136.40	$136.40
Purchase #6	$144.30	8.179%	$156.1023	$156.10	$156.10	$156.10
Purchase #7	$104.43	6.489%	$111.2065	$111.21	$111.20	$111.20
7 purchase totals =	$944.32		$1,017.4884	$1,017.49	$1,017.50	$1,017.40