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	$211.39	5.818%	$223.6887	$223.69	$223.70	$223.70
Purchase #2	$72.95	11.371%	$81.2451	$81.25	$81.25	$81.20
Purchase #3	$115.44	10.190%	$127.2033	$127.20	$127.20	$127.20
Purchase #4	$53.30	10.728%	$59.018	$59.02	$59.00	$59.00
Purchase #5	$61.54	8.489%	$66.7641	$66.76	$66.75	$66.80
Purchase #6	$7.50	5.711%	$7.9283	$7.93	$7.95	$7.90
Purchase #7	$103.54	7.185%	$110.9793	$110.98	$111.00	$111.00
7 purchase totals =	$625.66		$676.8268	$676.83	$676.85	$676.80