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	$98.73	7.563%	$106.1969	$106.20	$106.20	$106.20
Purchase #2	$12.53	4.687%	$13.1173	$13.12	$13.10	$13.10
Purchase #3	$183.41	6.286%	$194.9392	$194.94	$194.95	$194.90
Purchase #4	$179.75	5.793%	$190.1629	$190.16	$190.15	$190.20
Purchase #5	$50.26	10.133%	$55.3528	$55.35	$55.35	$55.40
Purchase #6	$90.75	9.251%	$99.1453	$99.15	$99.15	$99.10
Purchase #7	$115.30	6.764%	$123.0989	$123.10	$123.10	$123.10
7 purchase totals =	$730.73		$782.0133	$782.02	$782.00	$782.00