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	$82.30	3.825%	$85.448	$85.45	$85.45	$85.40
Purchase #2	$81.83	10.279%	$90.2413	$90.24	$90.25	$90.20
Purchase #3	$89.86	3.814%	$93.2873	$93.29	$93.30	$93.30
Purchase #4	$133.46	12.310%	$149.8889	$149.89	$149.90	$149.90
Purchase #5	$14.62	7.338%	$15.6928	$15.69	$15.70	$15.70
Purchase #6	$196.88	11.783%	$220.0784	$220.08	$220.10	$220.10
Purchase #7	$92.90	12.767%	$104.7605	$104.76	$104.75	$104.80
7 purchase totals =	$691.85		$759.3972	$759.40	$759.45	$759.40