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	$38.81	7.785%	$41.8314	$41.83	$41.85	$41.80
Purchase #2	$229.41	11.332%	$255.4067	$255.41	$255.40	$255.40
Purchase #3	$36.80	3.590%	$38.1211	$38.12	$38.10	$38.10
Purchase #4	$77.70	10.475%	$85.8391	$85.84	$85.85	$85.80
Purchase #5	$94.98	9.109%	$103.6317	$103.63	$103.65	$103.60
Purchase #6	$115.35	10.150%	$127.058	$127.06	$127.05	$127.10
Purchase #7	$242.28	12.674%	$272.9866	$272.99	$273.00	$273.00
7 purchase totals =	$835.33		$924.8746	$924.88	$924.90	$924.80