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	$202.31	10.413%	$223.3765	$223.38	$223.40	$223.40
Purchase #2	$244.72	9.523%	$268.0247	$268.02	$268.00	$268.00
Purchase #3	$64.97	9.329%	$71.0311	$71.03	$71.05	$71.00
Purchase #4	$42.80	5.255%	$45.0491	$45.05	$45.05	$45.00
Purchase #5	$75.83	7.295%	$81.3618	$81.36	$81.35	$81.40
Purchase #6	$186.98	7.295%	$200.6202	$200.62	$200.60	$200.60
Purchase #7	$136.50	11.643%	$152.3927	$152.39	$152.40	$152.40
7 purchase totals =	$954.11		$1,041.8561	$1,041.85	$1,041.85	$1,041.80