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	$101.89	3.445%	$105.4001	$105.40	$105.40	$105.40
Purchase #2	$161.30	13.380%	$182.8819	$182.88	$182.90	$182.90
Purchase #3	$123.44	5.663%	$130.4304	$130.43	$130.45	$130.40
Purchase #4	$227.70	13.452%	$258.3302	$258.33	$258.35	$258.30
Purchase #5	$245.46	10.337%	$270.8332	$270.83	$270.85	$270.80
Purchase #6	$85.65	4.474%	$89.482	$89.48	$89.50	$89.50
Purchase #7	$182.82	8.644%	$198.623	$198.62	$198.60	$198.60
7 purchase totals =	$1,128.26		$1,235.9808	$1,235.97	$1,236.05	$1,235.90