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	$184.42	5.640%	$194.8213	$194.82	$194.80	$194.80
Purchase #2	$38.46	9.499%	$42.1133	$42.11	$42.10	$42.10
Purchase #3	$219.88	10.261%	$242.4419	$242.44	$242.45	$242.40
Purchase #4	$119.35	10.128%	$131.4378	$131.44	$131.45	$131.40
Purchase #5	$105.67	12.483%	$118.8608	$118.86	$118.85	$118.90
Purchase #6	$92.65	7.198%	$99.3189	$99.32	$99.30	$99.30
Purchase #7	$192.78	7.390%	$207.0264	$207.03	$207.05	$207.00
7 purchase totals =	$953.21		$1,036.0204	$1,036.02	$1,036.00	$1,035.90