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	$54.56	4.196%	$56.8493	$56.85	$56.85	$56.80
Purchase #2	$248.84	6.272%	$264.4472	$264.45	$264.45	$264.40
Purchase #3	$59.60	13.470%	$67.6281	$67.63	$67.65	$67.60
Purchase #4	$240.84	7.755%	$259.5171	$259.52	$259.50	$259.50
Purchase #5	$122.26	3.854%	$126.9719	$126.97	$126.95	$127.00
Purchase #6	$73.60	13.573%	$83.5897	$83.59	$83.60	$83.60
Purchase #7	$193.51	13.330%	$219.3049	$219.30	$219.30	$219.30
7 purchase totals =	$993.21		$1,078.3082	$1,078.31	$1,078.30	$1,078.20