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	$184.91	5.154%	$194.4403	$194.44	$194.45	$194.40
Purchase #2	$145.91	3.594%	$151.154	$151.15	$151.15	$151.20
Purchase #3	$52.56	4.721%	$55.0414	$55.04	$55.05	$55.00
Purchase #4	$65.52	7.510%	$70.4406	$70.44	$70.45	$70.40
Purchase #5	$72.75	13.274%	$82.4068	$82.41	$82.40	$82.40
Purchase #6	$181.31	4.423%	$189.3293	$189.33	$189.35	$189.30
Purchase #7	$153.67	9.803%	$168.7343	$168.73	$168.75	$168.70
7 purchase totals =	$856.63		$911.5467	$911.54	$911.60	$911.40