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	$149.41	7.395%	$160.4589	$160.46	$160.45	$160.50
Purchase #2	$202.91	6.669%	$216.4421	$216.44	$216.45	$216.40
Purchase #3	$129.87	12.342%	$145.8986	$145.90	$145.90	$145.90
Purchase #4	$240.56	9.722%	$263.9472	$263.95	$263.95	$263.90
Purchase #5	$225.96	8.173%	$244.4277	$244.43	$244.45	$244.40
Purchase #6	$39.68	3.712%	$41.1529	$41.15	$41.15	$41.20
Purchase #7	$26.56	7.504%	$28.5531	$28.55	$28.55	$28.60
7 purchase totals =	$1,014.95		$1,100.8805	$1,100.88	$1,100.90	$1,100.90