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	$41.72	10.702%	$46.1849	$46.18	$46.20	$46.20
Purchase #2	$80.58	11.412%	$89.7758	$89.78	$89.80	$89.80
Purchase #3	$91.68	7.280%	$98.3543	$98.35	$98.35	$98.40
Purchase #4	$48.32	4.154%	$50.3272	$50.33	$50.35	$50.30
Purchase #5	$167.42	7.233%	$179.5295	$179.53	$179.55	$179.50
Purchase #6	$94.57	4.640%	$98.958	$98.96	$98.95	$99.00
Purchase #7	$147.42	12.419%	$165.7281	$165.73	$165.75	$165.70
7 purchase totals =	$671.71		$728.8578	$728.86	$728.95	$728.90