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	$174.37	6.522%	$185.7424	$185.74	$185.75	$185.70
Purchase #2	$206.78	8.446%	$224.2446	$224.24	$224.25	$224.20
Purchase #3	$100.64	6.826%	$107.5097	$107.51	$107.50	$107.50
Purchase #4	$250.69	4.180%	$261.1688	$261.17	$261.15	$261.20
Purchase #5	$16.61	10.689%	$18.3854	$18.39	$18.40	$18.40
Purchase #6	$88.81	6.351%	$94.4503	$94.45	$94.45	$94.50
Purchase #7	$175.61	7.373%	$188.5577	$188.56	$188.55	$188.60
7 purchase totals =	$1,013.51		$1,080.0589	$1,080.06	$1,080.05	$1,080.10