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	$113.77	9.473%	$124.5474	$124.55	$124.55	$124.50
Purchase #2	$88.73	11.488%	$98.9233	$98.92	$98.90	$98.90
Purchase #3	$39.72	6.106%	$42.1453	$42.15	$42.15	$42.10
Purchase #4	$190.52	12.136%	$213.6415	$213.64	$213.65	$213.60
Purchase #5	$71.41	12.600%	$80.4077	$80.41	$80.40	$80.40
Purchase #6	$232.47	4.364%	$242.615	$242.62	$242.60	$242.60
Purchase #7	$76.61	7.401%	$82.2799	$82.28	$82.30	$82.30
7 purchase totals =	$813.23		$884.5601	$884.57	$884.55	$884.40