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	$99.37	11.400%	$110.6982	$110.70	$110.70	$110.70
Purchase #2	$106.80	5.675%	$112.8609	$112.86	$112.85	$112.90
Purchase #3	$5.96	3.336%	$6.1588	$6.16	$6.15	$6.20
Purchase #4	$240.33	4.162%	$250.3325	$250.33	$250.35	$250.30
Purchase #5	$79.59	7.544%	$85.5943	$85.59	$85.60	$85.60
Purchase #6	$83.76	10.414%	$92.4828	$92.48	$92.50	$92.50
Purchase #7	$199.46	11.331%	$222.0608	$222.06	$222.05	$222.10
7 purchase totals =	$815.27		$880.1883	$880.18	$880.20	$880.30