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	$156.39	3.846%	$162.4048	$162.40	$162.40	$162.40
Purchase #2	$122.54	3.671%	$127.0384	$127.04	$127.05	$127.00
Purchase #3	$208.34	8.654%	$226.3697	$226.37	$226.35	$226.40
Purchase #4	$147.68	9.850%	$162.2265	$162.23	$162.25	$162.20
Purchase #5	$248.64	7.159%	$266.4401	$266.44	$266.45	$266.40
Purchase #6	$247.34	11.397%	$275.5293	$275.53	$275.55	$275.50
Purchase #7	$66.28	9.539%	$72.6024	$72.60	$72.60	$72.60
7 purchase totals =	$1,197.21		$1,292.6112	$1,292.61	$1,292.65	$1,292.50