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	$242.40	4.711%	$253.8195	$253.82	$253.80	$253.80
Purchase #2	$82.55	3.148%	$85.1487	$85.15	$85.15	$85.10
Purchase #3	$180.41	6.238%	$191.664	$191.66	$191.65	$191.70
Purchase #4	$107.33	7.713%	$115.6084	$115.61	$115.60	$115.60
Purchase #5	$93.51	13.399%	$106.0394	$106.04	$106.05	$106.00
Purchase #6	$62.52	5.870%	$66.1899	$66.19	$66.20	$66.20
Purchase #7	$181.96	9.304%	$198.8896	$198.89	$198.90	$198.90
7 purchase totals =	$950.68		$1,017.3595	$1,017.36	$1,017.35	$1,017.30