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	$193.81	9.523%	$212.2665	$212.27	$212.25	$212.30
Purchase #2	$141.61	4.778%	$148.3761	$148.38	$148.40	$148.40
Purchase #3	$120.48	10.426%	$133.0412	$133.04	$133.05	$133.00
Purchase #4	$208.87	7.201%	$223.9107	$223.91	$223.90	$223.90
Purchase #5	$187.27	10.288%	$206.5363	$206.54	$206.55	$206.50
Purchase #6	$29.95	8.817%	$32.5907	$32.59	$32.60	$32.60
Purchase #7	$141.73	7.285%	$152.055	$152.06	$152.05	$152.10
7 purchase totals =	$1,023.72		$1,108.7765	$1,108.79	$1,108.80	$1,108.80