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	$107.41	10.198%	$118.3637	$118.36	$118.35	$118.40
Purchase #2	$100.61	8.646%	$109.3087	$109.31	$109.30	$109.30
Purchase #3	$92.98	5.633%	$98.2176	$98.22	$98.20	$98.20
Purchase #4	$145.32	4.787%	$152.2765	$152.28	$152.30	$152.30
Purchase #5	$27.63	12.753%	$31.1537	$31.15	$31.15	$31.20
Purchase #6	$136.83	9.832%	$150.2831	$150.28	$150.30	$150.30
Purchase #7	$47.40	11.295%	$52.7538	$52.75	$52.75	$52.80
7 purchase totals =	$658.18		$712.3571	$712.35	$712.35	$712.50