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	$95.90	5.640%	$101.3088	$101.31	$101.30	$101.30
Purchase #2	$112.81	6.243%	$119.8527	$119.85	$119.85	$119.90
Purchase #3	$228.66	11.419%	$254.7707	$254.77	$254.75	$254.80
Purchase #4	$138.37	5.217%	$145.5888	$145.59	$145.60	$145.60
Purchase #5	$99.51	3.645%	$103.1371	$103.14	$103.15	$103.10
Purchase #6	$239.76	8.191%	$259.3987	$259.40	$259.40	$259.40
Purchase #7	$37.60	12.546%	$42.3173	$42.32	$42.30	$42.30
7 purchase totals =	$952.61		$1,026.3741	$1,026.38	$1,026.35	$1,026.40