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	$196.46	3.497%	$203.3302	$203.33	$203.35	$203.30
Purchase #2	$36.50	13.341%	$41.3695	$41.37	$41.35	$41.40
Purchase #3	$47.59	13.605%	$54.0646	$54.06	$54.05	$54.10
Purchase #4	$82.30	8.277%	$89.112	$89.11	$89.10	$89.10
Purchase #5	$243.60	10.250%	$268.569	$268.57	$268.55	$268.60
Purchase #6	$31.36	13.629%	$35.6341	$35.63	$35.65	$35.60
Purchase #7	$17.48	11.521%	$19.4939	$19.49	$19.50	$19.50
7 purchase totals =	$655.29		$711.5733	$711.56	$711.55	$711.60