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	$89.88	5.639%	$94.9483	$94.95	$94.95	$94.90
Purchase #2	$208.77	5.438%	$220.1229	$220.12	$220.10	$220.10
Purchase #3	$105.38	9.693%	$115.5945	$115.59	$115.60	$115.60
Purchase #4	$52.60	5.211%	$55.341	$55.34	$55.35	$55.30
Purchase #5	$53.90	9.658%	$59.1057	$59.11	$59.10	$59.10
Purchase #6	$149.30	7.544%	$160.5632	$160.56	$160.55	$160.60
Purchase #7	$77.54	11.347%	$86.3385	$86.34	$86.35	$86.30
7 purchase totals =	$737.37		$792.0141	$792.01	$792.00	$791.90