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	$191.52	9.400%	$209.5229	$209.52	$209.50	$209.50
Purchase #2	$38.25	6.623%	$40.7833	$40.78	$40.80	$40.80
Purchase #3	$118.70	3.851%	$123.2711	$123.27	$123.25	$123.30
Purchase #4	$37.69	4.754%	$39.4818	$39.48	$39.50	$39.50
Purchase #5	$64.47	11.835%	$72.1	$72.10	$72.10	$72.10
Purchase #6	$91.70	10.292%	$101.1378	$101.14	$101.15	$101.10
Purchase #7	$184.55	8.309%	$199.8843	$199.88	$199.90	$199.90
7 purchase totals =	$726.88		$786.1812	$786.17	$786.20	$786.20