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	$162.99	10.655%	$180.3566	$180.36	$180.35	$180.40
Purchase #2	$147.94	10.124%	$162.9174	$162.92	$162.90	$162.90
Purchase #3	$55.70	9.196%	$60.8222	$60.82	$60.80	$60.80
Purchase #4	$139.87	7.251%	$150.012	$150.01	$150.00	$150.00
Purchase #5	$246.55	10.743%	$273.0369	$273.04	$273.05	$273.00
Purchase #6	$231.97	13.495%	$263.2744	$263.27	$263.25	$263.30
Purchase #7	$80.91	10.133%	$89.1086	$89.11	$89.10	$89.10
7 purchase totals =	$1,065.93		$1,179.5281	$1,179.53	$1,179.45	$1,179.50