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	$45.74	5.623%	$48.312	$48.31	$48.30	$48.30
Purchase #2	$178.56	8.586%	$193.8912	$193.89	$193.90	$193.90
Purchase #3	$247.59	3.462%	$256.1616	$256.16	$256.15	$256.20
Purchase #4	$202.73	4.504%	$211.861	$211.86	$211.85	$211.90
Purchase #5	$116.80	9.115%	$127.4463	$127.45	$127.45	$127.40
Purchase #6	$101.84	7.499%	$109.477	$109.48	$109.50	$109.50
Purchase #7	$144.54	8.446%	$156.7478	$156.75	$156.75	$156.70
7 purchase totals =	$1,037.80		$1,103.8969	$1,103.90	$1,103.90	$1,103.90