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	$156.79	7.638%	$168.7656	$168.77	$168.75	$168.80
Purchase #2	$49.30	8.360%	$53.4215	$53.42	$53.40	$53.40
Purchase #3	$46.37	6.498%	$49.3831	$49.38	$49.40	$49.40
Purchase #4	$244.29	11.604%	$272.6374	$272.64	$272.65	$272.60
Purchase #5	$248.37	9.585%	$272.1763	$272.18	$272.20	$272.20
Purchase #6	$34.73	7.490%	$37.3313	$37.33	$37.35	$37.30
Purchase #7	$187.66	4.814%	$196.694	$196.69	$196.70	$196.70
7 purchase totals =	$967.51		$1,050.4092	$1,050.41	$1,050.45	$1,050.40