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	$51.41	8.802%	$55.9351	$55.94	$55.95	$55.90
Purchase #2	$104.36	8.836%	$113.5812	$113.58	$113.60	$113.60
Purchase #3	$180.87	5.758%	$191.2845	$191.28	$191.30	$191.30
Purchase #4	$130.46	12.862%	$147.2398	$147.24	$147.25	$147.20
Purchase #5	$182.38	5.141%	$191.7562	$191.76	$191.75	$191.80
Purchase #6	$206.51	13.139%	$233.6433	$233.64	$233.65	$233.60
Purchase #7	$189.62	11.230%	$210.9143	$210.91	$210.90	$210.90
7 purchase totals =	$1,045.61		$1,144.3544	$1,144.35	$1,144.40	$1,144.30