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	$145.83	4.854%	$152.9086	$152.91	$152.90	$152.90
Purchase #2	$139.46	4.173%	$145.2797	$145.28	$145.30	$145.30
Purchase #3	$87.26	10.627%	$96.5331	$96.53	$96.55	$96.50
Purchase #4	$197.94	13.457%	$224.5768	$224.58	$224.60	$224.60
Purchase #5	$84.63	6.635%	$90.2452	$90.25	$90.25	$90.20
Purchase #6	$84.71	10.674%	$93.7519	$93.75	$93.75	$93.80
Purchase #7	$85.66	4.758%	$89.7357	$89.74	$89.75	$89.70
7 purchase totals =	$825.49		$893.0310	$893.04	$893.10	$893.00