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	$145.93	13.375%	$165.4481	$165.45	$165.45	$165.40
Purchase #2	$215.71	13.779%	$245.4327	$245.43	$245.45	$245.40
Purchase #3	$192.75	11.651%	$215.2073	$215.21	$215.20	$215.20
Purchase #4	$47.73	6.473%	$50.8196	$50.82	$50.80	$50.80
Purchase #5	$53.86	10.212%	$59.3602	$59.36	$59.35	$59.40
Purchase #6	$123.33	5.627%	$130.2698	$130.27	$130.25	$130.30
Purchase #7	$165.40	9.218%	$180.6466	$180.65	$180.65	$180.60
7 purchase totals =	$944.71		$1,047.1843	$1,047.19	$1,047.15	$1,047.10