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	$177.63	3.802%	$184.3835	$184.38	$184.40	$184.40
Purchase #2	$233.50	5.577%	$246.5223	$246.52	$246.50	$246.50
Purchase #3	$135.55	8.105%	$146.5363	$146.54	$146.55	$146.50
Purchase #4	$118.79	13.241%	$134.519	$134.52	$134.50	$134.50
Purchase #5	$188.94	11.433%	$210.5415	$210.54	$210.55	$210.50
Purchase #6	$85.73	6.501%	$91.3033	$91.30	$91.30	$91.30
Purchase #7	$75.33	3.233%	$77.7654	$77.77	$77.75	$77.80
7 purchase totals =	$1,015.47		$1,091.5713	$1,091.57	$1,091.55	$1,091.50