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	$99.72	13.413%	$113.0954	$113.10	$113.10	$113.10
Purchase #2	$53.83	10.781%	$59.6334	$59.63	$59.65	$59.60
Purchase #3	$156.78	10.788%	$173.6934	$173.69	$173.70	$173.70
Purchase #4	$211.46	6.834%	$225.9112	$225.91	$225.90	$225.90
Purchase #5	$31.80	11.324%	$35.401	$35.40	$35.40	$35.40
Purchase #6	$228.60	13.473%	$259.3993	$259.40	$259.40	$259.40
Purchase #7	$170.31	6.588%	$181.53	$181.53	$181.55	$181.50
7 purchase totals =	$952.50		$1,048.6637	$1,048.66	$1,048.70	$1,048.60