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	$79.92	4.766%	$83.729	$83.73	$83.75	$83.70
Purchase #2	$229.77	4.212%	$239.4479	$239.45	$239.45	$239.40
Purchase #3	$105.54	6.804%	$112.7209	$112.72	$112.70	$112.70
Purchase #4	$110.47	6.234%	$117.3567	$117.36	$117.35	$117.40
Purchase #5	$82.94	7.567%	$89.2161	$89.22	$89.20	$89.20
Purchase #6	$238.47	10.376%	$263.2136	$263.21	$263.20	$263.20
Purchase #7	$101.46	4.814%	$106.3443	$106.34	$106.35	$106.30
7 purchase totals =	$948.57		$1,012.0285	$1,012.03	$1,012.00	$1,011.90