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	$130.90	10.820%	$145.0634	$145.06	$145.05	$145.10
Purchase #2	$245.36	5.804%	$259.6007	$259.60	$259.60	$259.60
Purchase #3	$174.90	12.133%	$196.1206	$196.12	$196.10	$196.10
Purchase #4	$48.99	9.513%	$53.6504	$53.65	$53.65	$53.70
Purchase #5	$111.65	10.358%	$123.2147	$123.21	$123.20	$123.20
Purchase #6	$250.75	10.293%	$276.5597	$276.56	$276.55	$276.60
Purchase #7	$66.37	4.129%	$69.1104	$69.11	$69.10	$69.10
7 purchase totals =	$1,028.92		$1,123.3199	$1,123.31	$1,123.25	$1,123.40