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	$238.43	10.350%	$263.1075	$263.11	$263.10	$263.10
Purchase #2	$104.68	4.143%	$109.0169	$109.02	$109.00	$109.00
Purchase #3	$28.52	11.669%	$31.848	$31.85	$31.85	$31.80
Purchase #4	$55.34	12.755%	$62.3986	$62.40	$62.40	$62.40
Purchase #5	$82.90	3.852%	$86.0933	$86.09	$86.10	$86.10
Purchase #6	$195.26	13.214%	$221.0617	$221.06	$221.05	$221.10
Purchase #7	$28.56	11.312%	$31.7907	$31.79	$31.80	$31.80
7 purchase totals =	$733.69		$805.3167	$805.32	$805.30	$805.30