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	$121.94	4.394%	$127.298	$127.30	$127.30	$127.30
Purchase #2	$223.54	8.443%	$242.4135	$242.41	$242.40	$242.40
Purchase #3	$108.43	3.862%	$112.6176	$112.62	$112.60	$112.60
Purchase #4	$41.61	12.421%	$46.7784	$46.78	$46.80	$46.80
Purchase #5	$49.80	8.140%	$53.8537	$53.85	$53.85	$53.90
Purchase #6	$62.57	7.251%	$67.107	$67.11	$67.10	$67.10
Purchase #7	$79.93	5.759%	$84.5332	$84.53	$84.55	$84.50
7 purchase totals =	$687.82		$734.6014	$734.60	$734.60	$734.60