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	$190.41	5.136%	$200.1895	$200.19	$200.20	$200.20
Purchase #2	$31.83	12.137%	$35.6932	$35.69	$35.70	$35.70
Purchase #3	$218.34	9.751%	$239.6303	$239.63	$239.65	$239.60
Purchase #4	$140.70	8.585%	$152.7791	$152.78	$152.80	$152.80
Purchase #5	$170.78	13.145%	$193.229	$193.23	$193.25	$193.20
Purchase #6	$171.80	4.112%	$178.8644	$178.86	$178.85	$178.90
Purchase #7	$72.91	13.688%	$82.8899	$82.89	$82.90	$82.90
7 purchase totals =	$996.77		$1,083.2754	$1,083.27	$1,083.35	$1,083.30