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	$172.66	7.135%	$184.9793	$184.98	$185.00	$185.00
Purchase #2	$136.28	4.494%	$142.4044	$142.40	$142.40	$142.40
Purchase #3	$219.54	8.767%	$238.7871	$238.79	$238.80	$238.80
Purchase #4	$163.49	13.254%	$185.159	$185.16	$185.15	$185.20
Purchase #5	$203.68	5.274%	$214.4221	$214.42	$214.40	$214.40
Purchase #6	$79.35	12.744%	$89.4624	$89.46	$89.45	$89.50
Purchase #7	$155.72	11.243%	$173.2276	$173.23	$173.25	$173.20
7 purchase totals =	$1,130.72		$1,228.4419	$1,228.44	$1,228.45	$1,228.50