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	$134.33	9.306%	$146.8307	$146.83	$146.85	$146.80
Purchase #2	$191.25	3.740%	$198.4028	$198.40	$198.40	$198.40
Purchase #3	$22.63	11.278%	$25.1822	$25.18	$25.20	$25.20
Purchase #4	$206.43	13.838%	$234.9958	$235.00	$235.00	$235.00
Purchase #5	$165.39	11.406%	$184.2544	$184.25	$184.25	$184.30
Purchase #6	$149.90	8.545%	$162.709	$162.71	$162.70	$162.70
Purchase #7	$141.60	4.441%	$147.8885	$147.89	$147.90	$147.90
7 purchase totals =	$1,011.53		$1,100.2634	$1,100.26	$1,100.30	$1,100.30