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	$95.93	4.609%	$100.3514	$100.35	$100.35	$100.40
Purchase #2	$96.84	9.167%	$105.7173	$105.72	$105.70	$105.70
Purchase #3	$18.51	5.618%	$19.5499	$19.55	$19.55	$19.50
Purchase #4	$169.76	5.760%	$179.5382	$179.54	$179.55	$179.50
Purchase #5	$162.64	13.501%	$184.598	$184.60	$184.60	$184.60
Purchase #6	$31.42	6.581%	$33.4878	$33.49	$33.50	$33.50
Purchase #7	$150.37	12.542%	$169.2294	$169.23	$169.25	$169.20
7 purchase totals =	$725.47		$792.4720	$792.48	$792.50	$792.40