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	$75.56	9.617%	$82.8266	$82.83	$82.85	$82.80
Purchase #2	$151.91	5.665%	$160.5157	$160.52	$160.50	$160.50
Purchase #3	$155.46	9.250%	$169.8401	$169.84	$169.85	$169.80
Purchase #4	$92.81	12.647%	$104.5477	$104.55	$104.55	$104.50
Purchase #5	$229.38	9.123%	$250.3063	$250.31	$250.30	$250.30
Purchase #6	$155.88	9.489%	$170.6715	$170.67	$170.65	$170.70
Purchase #7	$79.49	7.551%	$85.4923	$85.49	$85.50	$85.50
7 purchase totals =	$940.49		$1,024.2002	$1,024.21	$1,024.20	$1,024.10