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	$56.45	10.387%	$62.3135	$62.31	$62.30	$62.30
Purchase #2	$99.27	10.370%	$109.5643	$109.56	$109.55	$109.60
Purchase #3	$183.91	11.398%	$204.8721	$204.87	$204.85	$204.90
Purchase #4	$39.78	7.487%	$42.7583	$42.76	$42.75	$42.80
Purchase #5	$47.87	12.395%	$53.8035	$53.80	$53.80	$53.80
Purchase #6	$99.41	12.700%	$112.0351	$112.04	$112.05	$112.00
Purchase #7	$184.42	13.550%	$209.4089	$209.41	$209.40	$209.40
7 purchase totals =	$711.11		$794.7557	$794.75	$794.70	$794.80