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	$86.38	11.625%	$96.4217	$96.42	$96.40	$96.40
Purchase #2	$130.62	9.141%	$142.56	$142.56	$142.55	$142.60
Purchase #3	$59.45	12.708%	$67.0049	$67.00	$67.00	$67.00
Purchase #4	$154.55	10.821%	$171.2739	$171.27	$171.25	$171.30
Purchase #5	$79.30	9.595%	$86.9088	$86.91	$86.90	$86.90
Purchase #6	$125.39	13.202%	$141.944	$141.94	$141.95	$141.90
Purchase #7	$192.47	13.643%	$218.7287	$218.73	$218.75	$218.70
7 purchase totals =	$828.16		$924.8420	$924.83	$924.80	$924.80