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	$72.93	8.501%	$79.1298	$79.13	$79.15	$79.10
Purchase #2	$181.33	6.497%	$193.111	$193.11	$193.10	$193.10
Purchase #3	$130.56	9.442%	$142.8875	$142.89	$142.90	$142.90
Purchase #4	$233.75	9.429%	$255.7903	$255.79	$255.80	$255.80
Purchase #5	$106.94	5.309%	$112.6174	$112.62	$112.60	$112.60
Purchase #6	$47.83	7.593%	$51.4617	$51.46	$51.45	$51.50
Purchase #7	$229.54	5.313%	$241.7355	$241.74	$241.75	$241.70
7 purchase totals =	$1,002.88		$1,076.7332	$1,076.74	$1,076.75	$1,076.70