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	$94.69	7.828%	$102.1023	$102.10	$102.10	$102.10
Purchase #2	$170.66	5.317%	$179.734	$179.73	$179.75	$179.70
Purchase #3	$80.92	11.416%	$90.1578	$90.16	$90.15	$90.20
Purchase #4	$33.46	3.275%	$34.5558	$34.56	$34.55	$34.60
Purchase #5	$160.33	4.823%	$168.0627	$168.06	$168.05	$168.10
Purchase #6	$103.88	9.569%	$113.8203	$113.82	$113.80	$113.80
Purchase #7	$159.88	3.773%	$165.9123	$165.91	$165.90	$165.90
7 purchase totals =	$803.82		$854.3452	$854.34	$854.30	$854.40