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	$137.27	7.479%	$147.5364	$147.54	$147.55	$147.50
Purchase #2	$182.62	7.322%	$195.9914	$195.99	$196.00	$196.00
Purchase #3	$104.77	6.526%	$111.6073	$111.61	$111.60	$111.60
Purchase #4	$156.38	11.399%	$174.2058	$174.21	$174.20	$174.20
Purchase #5	$152.35	11.637%	$170.079	$170.08	$170.10	$170.10
Purchase #6	$104.79	4.308%	$109.3044	$109.30	$109.30	$109.30
Purchase #7	$179.98	4.309%	$187.7353	$187.74	$187.75	$187.70
7 purchase totals =	$1,018.16		$1,096.4596	$1,096.47	$1,096.50	$1,096.40