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	$184.44	9.573%	$202.0964	$202.10	$202.10	$202.10
Purchase #2	$127.52	13.293%	$144.4712	$144.47	$144.45	$144.50
Purchase #3	$153.54	5.778%	$162.4115	$162.41	$162.40	$162.40
Purchase #4	$99.32	10.464%	$109.7128	$109.71	$109.70	$109.70
Purchase #5	$104.52	9.321%	$114.2623	$114.26	$114.25	$114.30
Purchase #6	$134.32	3.821%	$139.4524	$139.45	$139.45	$139.50
Purchase #7	$124.89	12.157%	$140.0729	$140.07	$140.05	$140.10
7 purchase totals =	$928.55		$1,012.4795	$1,012.47	$1,012.40	$1,012.60