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	$47.73	10.251%	$52.6228	$52.62	$52.60	$52.60
Purchase #2	$91.39	13.293%	$103.5385	$103.54	$103.55	$103.50
Purchase #3	$221.76	7.816%	$239.0928	$239.09	$239.10	$239.10
Purchase #4	$26.41	4.393%	$27.5702	$27.57	$27.55	$27.60
Purchase #5	$19.82	6.236%	$21.056	$21.06	$21.05	$21.10
Purchase #6	$101.66	3.468%	$105.1856	$105.19	$105.20	$105.20
Purchase #7	$238.54	6.298%	$253.5632	$253.56	$253.55	$253.60
7 purchase totals =	$747.31		$802.6291	$802.63	$802.60	$802.70