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	$71.34	6.737%	$76.1462	$76.15	$76.15	$76.10
Purchase #2	$163.93	5.495%	$172.938	$172.94	$172.95	$172.90
Purchase #3	$128.79	6.691%	$137.4073	$137.41	$137.40	$137.40
Purchase #4	$142.30	3.355%	$147.0742	$147.07	$147.05	$147.10
Purchase #5	$6.72	9.385%	$7.3507	$7.35	$7.35	$7.40
Purchase #6	$64.86	4.679%	$67.8948	$67.89	$67.90	$67.90
Purchase #7	$168.36	9.294%	$184.0074	$184.01	$184.00	$184.00
7 purchase totals =	$746.30		$792.8186	$792.82	$792.80	$792.80