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	$232.54	4.349%	$242.6532	$242.65	$242.65	$242.70
Purchase #2	$166.38	13.748%	$189.2539	$189.25	$189.25	$189.30
Purchase #3	$113.64	3.523%	$117.6435	$117.64	$117.65	$117.60
Purchase #4	$64.43	12.228%	$72.3085	$72.31	$72.30	$72.30
Purchase #5	$180.34	5.268%	$189.8403	$189.84	$189.85	$189.80
Purchase #6	$244.73	11.600%	$273.1187	$273.12	$273.10	$273.10
Purchase #7	$202.27	10.432%	$223.3708	$223.37	$223.35	$223.40
7 purchase totals =	$1,204.33		$1,308.1889	$1,308.18	$1,308.15	$1,308.20