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	$209.76	6.445%	$223.279	$223.28	$223.30	$223.30
Purchase #2	$70.65	4.120%	$73.5608	$73.56	$73.55	$73.60
Purchase #3	$80.40	11.586%	$89.7151	$89.72	$89.70	$89.70
Purchase #4	$33.87	11.132%	$37.6404	$37.64	$37.65	$37.60
Purchase #5	$58.84	7.136%	$63.0388	$63.04	$63.05	$63.00
Purchase #6	$82.32	12.664%	$92.745	$92.75	$92.75	$92.70
Purchase #7	$178.51	6.165%	$189.5151	$189.52	$189.50	$189.50
7 purchase totals =	$714.35		$769.4942	$769.51	$769.50	$769.40