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	$188.35	13.782%	$214.3084	$214.31	$214.30	$214.30
Purchase #2	$62.75	13.684%	$71.3367	$71.34	$71.35	$71.30
Purchase #3	$74.55	10.476%	$82.3599	$82.36	$82.35	$82.40
Purchase #4	$113.36	12.609%	$127.6536	$127.65	$127.65	$127.70
Purchase #5	$105.59	4.445%	$110.2835	$110.28	$110.30	$110.30
Purchase #6	$85.67	6.183%	$90.967	$90.97	$90.95	$91.00
Purchase #7	$172.83	3.413%	$178.7287	$178.73	$178.75	$178.70
7 purchase totals =	$803.10		$875.6378	$875.64	$875.65	$875.70