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	$162.37	3.254%	$167.6535	$167.65	$167.65	$167.70
Purchase #2	$182.89	3.560%	$189.4009	$189.40	$189.40	$189.40
Purchase #3	$99.92	9.528%	$109.4404	$109.44	$109.45	$109.40
Purchase #4	$17.25	3.672%	$17.8834	$17.88	$17.90	$17.90
Purchase #5	$217.59	11.452%	$242.5084	$242.51	$242.50	$242.50
Purchase #6	$241.86	4.744%	$253.3338	$253.33	$253.35	$253.30
Purchase #7	$67.91	6.274%	$72.1707	$72.17	$72.15	$72.20
7 purchase totals =	$989.79		$1,052.3911	$1,052.38	$1,052.40	$1,052.40