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	$171.69	11.627%	$191.6524	$191.65	$191.65	$191.70
Purchase #2	$72.47	13.728%	$82.4187	$82.42	$82.40	$82.40
Purchase #3	$96.49	13.138%	$109.1669	$109.17	$109.15	$109.20
Purchase #4	$208.65	11.207%	$232.0334	$232.03	$232.05	$232.00
Purchase #5	$105.53	4.586%	$110.3696	$110.37	$110.35	$110.40
Purchase #6	$232.87	6.199%	$247.3056	$247.31	$247.30	$247.30
Purchase #7	$39.50	12.613%	$44.4821	$44.48	$44.50	$44.50
7 purchase totals =	$927.20		$1,017.4287	$1,017.43	$1,017.40	$1,017.50