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	$176.89	4.318%	$184.5281	$184.53	$184.55	$184.50
Purchase #2	$85.56	10.453%	$94.5036	$94.50	$94.50	$94.50
Purchase #3	$94.79	12.287%	$106.4368	$106.44	$106.45	$106.40
Purchase #4	$90.26	4.330%	$94.1683	$94.17	$94.15	$94.20
Purchase #5	$202.89	10.385%	$223.9601	$223.96	$223.95	$224.00
Purchase #6	$36.89	13.113%	$41.7274	$41.73	$41.75	$41.70
Purchase #7	$147.73	13.262%	$167.322	$167.32	$167.30	$167.30
7 purchase totals =	$835.01		$912.6463	$912.65	$912.65	$912.60