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	$179.37	5.107%	$188.5304	$188.53	$188.55	$188.50
Purchase #2	$45.32	8.183%	$49.0285	$49.03	$49.05	$49.00
Purchase #3	$62.44	4.808%	$65.4421	$65.44	$65.45	$65.40
Purchase #4	$151.46	12.651%	$170.6212	$170.62	$170.60	$170.60
Purchase #5	$165.64	12.449%	$186.2605	$186.26	$186.25	$186.30
Purchase #6	$247.34	4.600%	$258.7176	$258.72	$258.70	$258.70
Purchase #7	$150.74	11.352%	$167.852	$167.85	$167.85	$167.90
7 purchase totals =	$1,002.31		$1,086.4523	$1,086.45	$1,086.45	$1,086.40