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	$189.45	3.586%	$196.2437	$196.24	$196.25	$196.20
Purchase #2	$103.77	5.831%	$109.8208	$109.82	$109.80	$109.80
Purchase #3	$118.57	13.784%	$134.9137	$134.91	$134.90	$134.90
Purchase #4	$216.33	5.111%	$227.3866	$227.39	$227.40	$227.40
Purchase #5	$190.45	8.651%	$206.9258	$206.93	$206.95	$206.90
Purchase #6	$58.29	3.668%	$60.4281	$60.43	$60.45	$60.40
Purchase #7	$178.38	5.865%	$188.842	$188.84	$188.85	$188.80
7 purchase totals =	$1,055.24		$1,124.5607	$1,124.56	$1,124.60	$1,124.40