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	$159.91	7.696%	$172.2167	$172.22	$172.20	$172.20
Purchase #2	$11.55	6.538%	$12.3051	$12.31	$12.30	$12.30
Purchase #3	$54.96	3.300%	$56.7737	$56.77	$56.75	$56.80
Purchase #4	$46.59	12.689%	$52.5018	$52.50	$52.50	$52.50
Purchase #5	$73.85	12.571%	$83.1337	$83.13	$83.15	$83.10
Purchase #6	$65.87	5.234%	$69.3176	$69.32	$69.30	$69.30
Purchase #7	$198.33	13.103%	$224.3172	$224.32	$224.30	$224.30
7 purchase totals =	$611.06		$670.5658	$670.57	$670.50	$670.50