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	$124.73	7.343%	$133.8889	$133.89	$133.90	$133.90
Purchase #2	$168.41	12.490%	$189.4444	$189.44	$189.45	$189.40
Purchase #3	$65.35	3.582%	$67.6908	$67.69	$67.70	$67.70
Purchase #4	$229.86	3.787%	$238.5648	$238.56	$238.55	$238.60
Purchase #5	$80.30	12.406%	$90.262	$90.26	$90.25	$90.30
Purchase #6	$248.52	11.319%	$276.65	$276.65	$276.65	$276.70
Purchase #7	$249.28	6.264%	$264.8949	$264.89	$264.90	$264.90
7 purchase totals =	$1,166.45		$1,261.3958	$1,261.38	$1,261.40	$1,261.50