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	$114.72	4.805%	$120.2323	$120.23	$120.25	$120.20
Purchase #2	$162.75	11.721%	$181.8259	$181.83	$181.85	$181.80
Purchase #3	$205.61	11.612%	$229.4854	$229.49	$229.50	$229.50
Purchase #4	$60.90	5.743%	$64.3975	$64.40	$64.40	$64.40
Purchase #5	$56.42	4.665%	$59.052	$59.05	$59.05	$59.10
Purchase #6	$163.57	3.122%	$168.6767	$168.68	$168.70	$168.70
Purchase #7	$238.50	5.200%	$250.902	$250.90	$250.90	$250.90
7 purchase totals =	$1,002.47		$1,074.5718	$1,074.58	$1,074.65	$1,074.60