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	$44.31	10.450%	$48.9404	$48.94	$48.95	$48.90
Purchase #2	$206.27	4.499%	$215.5501	$215.55	$215.55	$215.60
Purchase #3	$114.55	11.599%	$127.8367	$127.84	$127.85	$127.80
Purchase #4	$249.62	9.130%	$272.4103	$272.41	$272.40	$272.40
Purchase #5	$55.32	11.729%	$61.8085	$61.81	$61.80	$61.80
Purchase #6	$124.86	4.209%	$130.1154	$130.12	$130.10	$130.10
Purchase #7	$216.98	11.632%	$242.2191	$242.22	$242.20	$242.20
7 purchase totals =	$1,011.91		$1,098.8805	$1,098.89	$1,098.85	$1,098.80