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	$198.49	3.470%	$205.3776	$205.38	$205.40	$205.40
Purchase #2	$107.34	6.805%	$114.6445	$114.64	$114.65	$114.60
Purchase #3	$71.48	9.379%	$78.1841	$78.18	$78.20	$78.20
Purchase #4	$75.72	5.371%	$79.7869	$79.79	$79.80	$79.80
Purchase #5	$190.26	11.288%	$211.7365	$211.74	$211.75	$211.70
Purchase #6	$142.98	7.274%	$153.3804	$153.38	$153.40	$153.40
Purchase #7	$200.90	8.776%	$218.531	$218.53	$218.55	$218.50
7 purchase totals =	$987.17		$1,061.6410	$1,061.64	$1,061.75	$1,061.60