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	$72.59	13.562%	$82.4347	$82.43	$82.45	$82.40
Purchase #2	$114.31	11.437%	$127.3836	$127.38	$127.40	$127.40
Purchase #3	$130.45	6.843%	$139.3767	$139.38	$139.40	$139.40
Purchase #4	$241.92	8.813%	$263.2404	$263.24	$263.25	$263.20
Purchase #5	$220.51	7.374%	$236.7704	$236.77	$236.75	$236.80
Purchase #6	$231.79	4.412%	$242.0166	$242.02	$242.00	$242.00
Purchase #7	$39.56	7.557%	$42.5495	$42.55	$42.55	$42.50
7 purchase totals =	$1,051.13		$1,133.7719	$1,133.77	$1,133.80	$1,133.70