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	$207.58	6.199%	$220.4479	$220.45	$220.45	$220.40
Purchase #2	$83.41	7.183%	$89.4013	$89.40	$89.40	$89.40
Purchase #3	$166.76	4.706%	$174.6077	$174.61	$174.60	$174.60
Purchase #4	$179.36	13.861%	$204.2211	$204.22	$204.20	$204.20
Purchase #5	$34.30	4.719%	$35.9186	$35.92	$35.90	$35.90
Purchase #6	$64.56	11.404%	$71.9224	$71.92	$71.90	$71.90
Purchase #7	$215.73	12.416%	$242.515	$242.52	$242.50	$242.50
7 purchase totals =	$951.70		$1,039.0340	$1,039.04	$1,038.95	$1,038.90