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	$210.96	8.418%	$228.7186	$228.72	$228.70	$228.70
Purchase #2	$85.91	3.666%	$89.0595	$89.06	$89.05	$89.10
Purchase #3	$233.72	3.406%	$241.6805	$241.68	$241.70	$241.70
Purchase #4	$239.50	11.426%	$266.8653	$266.87	$266.85	$266.90
Purchase #5	$71.38	10.184%	$78.6493	$78.65	$78.65	$78.60
Purchase #6	$152.33	7.362%	$163.5445	$163.54	$163.55	$163.50
Purchase #7	$56.85	10.251%	$62.6777	$62.68	$62.70	$62.70
7 purchase totals =	$1,050.65		$1,131.1954	$1,131.20	$1,131.20	$1,131.20