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	$96.96	3.849%	$100.692	$100.69	$100.70	$100.70
Purchase #2	$110.41	11.501%	$123.1083	$123.11	$123.10	$123.10
Purchase #3	$83.62	9.255%	$91.359	$91.36	$91.35	$91.40
Purchase #4	$37.81	3.774%	$39.2369	$39.24	$39.25	$39.20
Purchase #5	$158.97	12.600%	$179.0002	$179.00	$179.00	$179.00
Purchase #6	$219.70	6.185%	$233.2884	$233.29	$233.30	$233.30
Purchase #7	$42.47	12.326%	$47.7049	$47.70	$47.70	$47.70
7 purchase totals =	$749.94		$814.3897	$814.39	$814.40	$814.40