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	$215.34	3.815%	$223.5552	$223.56	$223.55	$223.60
Purchase #2	$54.56	11.662%	$60.9228	$60.92	$60.90	$60.90
Purchase #3	$157.47	7.631%	$169.4865	$169.49	$169.50	$169.50
Purchase #4	$110.83	11.223%	$123.2685	$123.27	$123.25	$123.30
Purchase #5	$236.52	10.518%	$261.3972	$261.40	$261.40	$261.40
Purchase #6	$242.41	11.440%	$270.1417	$270.14	$270.15	$270.10
Purchase #7	$246.88	6.774%	$263.6037	$263.60	$263.60	$263.60
7 purchase totals =	$1,264.01		$1,372.3756	$1,372.38	$1,372.35	$1,372.40