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	$231.93	9.520%	$254.0097	$254.01	$254.00	$254.00
Purchase #2	$218.60	9.816%	$240.0578	$240.06	$240.05	$240.10
Purchase #3	$121.43	4.765%	$127.2161	$127.22	$127.20	$127.20
Purchase #4	$81.36	11.677%	$90.8604	$90.86	$90.85	$90.90
Purchase #5	$178.34	13.865%	$203.0668	$203.07	$203.05	$203.10
Purchase #6	$161.41	12.209%	$181.1165	$181.12	$181.10	$181.10
Purchase #7	$50.62	11.191%	$56.2849	$56.28	$56.30	$56.30
7 purchase totals =	$1,043.69		$1,152.6122	$1,152.62	$1,152.55	$1,152.70