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	$69.58	5.319%	$73.281	$73.28	$73.30	$73.30
Purchase #2	$19.55	3.684%	$20.2702	$20.27	$20.25	$20.30
Purchase #3	$206.32	12.118%	$231.3219	$231.32	$231.30	$231.30
Purchase #4	$35.76	4.253%	$37.2809	$37.28	$37.30	$37.30
Purchase #5	$59.67	8.587%	$64.7939	$64.79	$64.80	$64.80
Purchase #6	$176.37	3.284%	$182.162	$182.16	$182.15	$182.20
Purchase #7	$122.31	3.836%	$127.0018	$127.00	$127.00	$127.00
7 purchase totals =	$689.56		$736.1117	$736.10	$736.10	$736.20