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	$72.84	9.496%	$79.7569	$79.76	$79.75	$79.80
Purchase #2	$72.80	4.361%	$75.9748	$75.97	$75.95	$76.00
Purchase #3	$40.39	12.111%	$45.2816	$45.28	$45.30	$45.30
Purchase #4	$88.53	12.595%	$99.6804	$99.68	$99.70	$99.70
Purchase #5	$33.49	7.501%	$36.0021	$36.00	$36.00	$36.00
Purchase #6	$195.88	9.180%	$213.8618	$213.86	$213.85	$213.90
Purchase #7	$102.38	7.279%	$109.8322	$109.83	$109.85	$109.80
7 purchase totals =	$606.31		$660.3898	$660.38	$660.40	$660.50