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	$175.31	12.674%	$197.5288	$197.53	$197.55	$197.50
Purchase #2	$52.61	12.747%	$59.3162	$59.32	$59.30	$59.30
Purchase #3	$65.36	3.656%	$67.7496	$67.75	$67.75	$67.70
Purchase #4	$146.94	10.767%	$162.761	$162.76	$162.75	$162.80
Purchase #5	$76.40	13.666%	$86.8408	$86.84	$86.85	$86.80
Purchase #6	$90.91	3.760%	$94.3282	$94.33	$94.35	$94.30
Purchase #7	$144.68	12.191%	$162.3179	$162.32	$162.30	$162.30
7 purchase totals =	$752.21		$830.8425	$830.85	$830.85	$830.70