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	$134.28	4.819%	$140.751	$140.75	$140.75	$140.80
Purchase #2	$186.49	6.447%	$198.513	$198.51	$198.50	$198.50
Purchase #3	$83.91	5.467%	$88.4974	$88.50	$88.50	$88.50
Purchase #4	$7.43	7.139%	$7.9604	$7.96	$7.95	$8.00
Purchase #5	$220.88	8.843%	$240.4124	$240.41	$240.40	$240.40
Purchase #6	$103.32	6.112%	$109.6349	$109.63	$109.65	$109.60
Purchase #7	$105.65	5.696%	$111.6678	$111.67	$111.65	$111.70
7 purchase totals =	$841.96		$897.4369	$897.43	$897.40	$897.50