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	$164.82	6.117%	$174.902	$174.90	$174.90	$174.90
Purchase #2	$165.50	8.224%	$179.1107	$179.11	$179.10	$179.10
Purchase #3	$90.31	13.102%	$102.1424	$102.14	$102.15	$102.10
Purchase #4	$74.31	8.168%	$80.3796	$80.38	$80.40	$80.40
Purchase #5	$180.53	3.435%	$186.7312	$186.73	$186.75	$186.70
Purchase #6	$101.82	7.314%	$109.2671	$109.27	$109.25	$109.30
Purchase #7	$189.65	4.741%	$198.6413	$198.64	$198.65	$198.60
7 purchase totals =	$966.94		$1,031.1743	$1,031.17	$1,031.20	$1,031.10