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	$67.89	5.573%	$71.6735	$71.67	$71.65	$71.70
Purchase #2	$243.47	4.466%	$254.3434	$254.34	$254.35	$254.30
Purchase #3	$152.78	12.183%	$171.3932	$171.39	$171.40	$171.40
Purchase #4	$52.61	3.423%	$54.4108	$54.41	$54.40	$54.40
Purchase #5	$233.34	5.187%	$245.4433	$245.44	$245.45	$245.40
Purchase #6	$18.79	10.258%	$20.7175	$20.72	$20.70	$20.70
Purchase #7	$174.38	13.752%	$198.3607	$198.36	$198.35	$198.40
7 purchase totals =	$943.26		$1,016.3424	$1,016.33	$1,016.30	$1,016.30