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	$147.65	6.381%	$157.0715	$157.07	$157.05	$157.10
Purchase #2	$91.81	5.175%	$96.5612	$96.56	$96.55	$96.60
Purchase #3	$135.59	6.564%	$144.4901	$144.49	$144.50	$144.50
Purchase #4	$115.26	4.745%	$120.7291	$120.73	$120.75	$120.70
Purchase #5	$31.82	6.346%	$33.8393	$33.84	$33.85	$33.80
Purchase #6	$55.66	6.330%	$59.1833	$59.18	$59.20	$59.20
Purchase #7	$150.72	6.250%	$160.14	$160.14	$160.15	$160.10
7 purchase totals =	$728.51		$772.0145	$772.01	$772.05	$772.00