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	$240.45	11.152%	$267.265	$267.27	$267.25	$267.30
Purchase #2	$130.49	11.276%	$145.2041	$145.20	$145.20	$145.20
Purchase #3	$186.54	5.211%	$196.2606	$196.26	$196.25	$196.30
Purchase #4	$100.28	9.205%	$109.5108	$109.51	$109.50	$109.50
Purchase #5	$26.61	13.850%	$30.2955	$30.30	$30.30	$30.30
Purchase #6	$25.56	7.440%	$27.4617	$27.46	$27.45	$27.50
Purchase #7	$100.90	9.807%	$110.7953	$110.80	$110.80	$110.80
7 purchase totals =	$810.83		$886.7930	$886.80	$886.75	$886.90