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	$114.94	12.459%	$129.2604	$129.26	$129.25	$129.30
Purchase #2	$184.59	5.424%	$194.6022	$194.60	$194.60	$194.60
Purchase #3	$67.79	6.502%	$72.1977	$72.20	$72.20	$72.20
Purchase #4	$105.39	5.504%	$111.1907	$111.19	$111.20	$111.20
Purchase #5	$89.49	11.776%	$100.0283	$100.03	$100.05	$100.00
Purchase #6	$74.41	5.432%	$78.452	$78.45	$78.45	$78.50
Purchase #7	$246.97	6.546%	$263.1367	$263.14	$263.15	$263.10
7 purchase totals =	$883.58		$948.8680	$948.87	$948.90	$948.90