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	$198.29	7.134%	$212.436	$212.44	$212.45	$212.40
Purchase #2	$28.52	9.660%	$31.275	$31.28	$31.30	$31.30
Purchase #3	$249.56	8.839%	$271.6186	$271.62	$271.60	$271.60
Purchase #4	$39.54	6.542%	$42.1267	$42.13	$42.15	$42.10
Purchase #5	$97.30	11.168%	$108.1665	$108.17	$108.15	$108.20
Purchase #6	$175.73	9.351%	$192.1625	$192.16	$192.15	$192.20
Purchase #7	$147.46	10.236%	$162.554	$162.55	$162.55	$162.60
7 purchase totals =	$936.40		$1,020.3393	$1,020.35	$1,020.35	$1,020.40