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	$64.50	12.763%	$72.7321	$72.73	$72.75	$72.70
Purchase #2	$169.77	3.254%	$175.2943	$175.29	$175.30	$175.30
Purchase #3	$84.86	8.575%	$92.1367	$92.14	$92.15	$92.10
Purchase #4	$39.72	12.745%	$44.7823	$44.78	$44.80	$44.80
Purchase #5	$136.38	6.292%	$144.961	$144.96	$144.95	$145.00
Purchase #6	$211.78	5.453%	$223.3284	$223.33	$223.35	$223.30
Purchase #7	$108.95	5.839%	$115.3116	$115.31	$115.30	$115.30
7 purchase totals =	$815.96		$868.5464	$868.54	$868.60	$868.50