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	$159.37	11.535%	$177.7533	$177.75	$177.75	$177.80
Purchase #2	$31.33	12.567%	$35.2672	$35.27	$35.25	$35.30
Purchase #3	$118.69	10.421%	$131.0587	$131.06	$131.05	$131.10
Purchase #4	$77.61	11.550%	$86.574	$86.57	$86.55	$86.60
Purchase #5	$64.46	12.810%	$72.7173	$72.72	$72.70	$72.70
Purchase #6	$31.43	8.869%	$34.2175	$34.22	$34.20	$34.20
Purchase #7	$93.73	4.688%	$98.1241	$98.12	$98.10	$98.10
7 purchase totals =	$576.62		$635.7121	$635.71	$635.60	$635.80