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	$74.90	9.822%	$82.2567	$82.26	$82.25	$82.30
Purchase #2	$197.79	10.490%	$218.5382	$218.54	$218.55	$218.50
Purchase #3	$246.41	10.748%	$272.8941	$272.89	$272.90	$272.90
Purchase #4	$139.73	12.249%	$156.8455	$156.85	$156.85	$156.80
Purchase #5	$77.36	10.234%	$85.277	$85.28	$85.30	$85.30
Purchase #6	$81.27	11.140%	$90.3235	$90.32	$90.30	$90.30
Purchase #7	$147.44	8.601%	$160.1213	$160.12	$160.10	$160.10
7 purchase totals =	$964.90		$1,066.2563	$1,066.26	$1,066.25	$1,066.20