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	$101.71	6.223%	$108.0394	$108.04	$108.05	$108.00
Purchase #2	$175.51	11.819%	$196.2535	$196.25	$196.25	$196.30
Purchase #3	$120.83	3.237%	$124.7413	$124.74	$124.75	$124.70
Purchase #4	$31.56	13.224%	$35.7335	$35.73	$35.75	$35.70
Purchase #5	$231.52	7.234%	$248.2682	$248.27	$248.25	$248.30
Purchase #6	$111.69	7.650%	$120.2343	$120.23	$120.25	$120.20
Purchase #7	$89.52	7.783%	$96.4873	$96.49	$96.50	$96.50
7 purchase totals =	$862.34		$929.7575	$929.75	$929.80	$929.70