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	$36.27	4.607%	$37.941	$37.94	$37.95	$37.90
Purchase #2	$27.92	5.172%	$29.364	$29.36	$29.35	$29.40
Purchase #3	$85.92	5.112%	$90.3122	$90.31	$90.30	$90.30
Purchase #4	$161.82	5.696%	$171.0373	$171.04	$171.05	$171.00
Purchase #5	$142.87	12.361%	$160.5302	$160.53	$160.55	$160.50
Purchase #6	$61.34	13.468%	$69.6013	$69.60	$69.60	$69.60
Purchase #7	$72.46	3.169%	$74.7563	$74.76	$74.75	$74.80
7 purchase totals =	$588.60		$633.5423	$633.54	$633.55	$633.50