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	$189.69	3.573%	$196.4676	$196.47	$196.45	$196.50
Purchase #2	$81.95	5.395%	$86.3712	$86.37	$86.35	$86.40
Purchase #3	$210.33	4.705%	$220.226	$220.23	$220.25	$220.20
Purchase #4	$99.46	5.736%	$105.165	$105.17	$105.15	$105.20
Purchase #5	$6.26	10.459%	$6.9147	$6.91	$6.90	$6.90
Purchase #6	$65.36	5.583%	$69.009	$69.01	$69.00	$69.00
Purchase #7	$96.75	8.867%	$105.3288	$105.33	$105.35	$105.30
7 purchase totals =	$749.80		$789.4823	$789.49	$789.45	$789.50