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	$144.59	5.214%	$152.1289	$152.13	$152.15	$152.10
Purchase #2	$48.98	7.803%	$52.8019	$52.80	$52.80	$52.80
Purchase #3	$59.39	9.699%	$65.1502	$65.15	$65.15	$65.20
Purchase #4	$209.70	6.607%	$223.5549	$223.55	$223.55	$223.60
Purchase #5	$71.65	7.564%	$77.0696	$77.07	$77.05	$77.10
Purchase #6	$163.45	13.869%	$186.1189	$186.12	$186.10	$186.10
Purchase #7	$225.96	12.850%	$254.9959	$255.00	$255.00	$255.00
7 purchase totals =	$923.72		$1,011.8203	$1,011.82	$1,011.80	$1,011.90