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	$174.57	8.791%	$189.9164	$189.92	$189.90	$189.90
Purchase #2	$17.99	8.474%	$19.5145	$19.51	$19.50	$19.50
Purchase #3	$69.36	13.707%	$78.8672	$78.87	$78.85	$78.90
Purchase #4	$105.90	3.825%	$109.9507	$109.95	$109.95	$110.00
Purchase #5	$60.37	11.532%	$67.3319	$67.33	$67.35	$67.30
Purchase #6	$130.52	7.599%	$140.4382	$140.44	$140.45	$140.40
Purchase #7	$55.94	10.534%	$61.8327	$61.83	$61.85	$61.80
7 purchase totals =	$614.65		$667.8516	$667.85	$667.85	$667.80