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	$250.84	5.574%	$264.8218	$264.82	$264.80	$264.80
Purchase #2	$135.63	7.258%	$145.474	$145.47	$145.45	$145.50
Purchase #3	$211.32	4.640%	$221.1252	$221.13	$221.15	$221.10
Purchase #4	$142.55	3.414%	$147.4167	$147.42	$147.40	$147.40
Purchase #5	$153.61	12.281%	$172.4748	$172.47	$172.45	$172.50
Purchase #6	$67.99	7.450%	$73.0553	$73.06	$73.05	$73.10
Purchase #7	$113.31	8.609%	$123.0649	$123.06	$123.05	$123.10
7 purchase totals =	$1,075.25		$1,147.4327	$1,147.43	$1,147.35	$1,147.50