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	$131.32	8.302%	$142.2222	$142.22	$142.20	$142.20
Purchase #2	$120.28	4.171%	$125.2969	$125.30	$125.30	$125.30
Purchase #3	$172.95	8.765%	$188.1091	$188.11	$188.10	$188.10
Purchase #4	$231.77	3.518%	$239.9237	$239.92	$239.90	$239.90
Purchase #5	$196.79	13.501%	$223.3586	$223.36	$223.35	$223.40
Purchase #6	$86.25	11.126%	$95.8462	$95.85	$95.85	$95.80
Purchase #7	$79.56	8.204%	$86.0871	$86.09	$86.10	$86.10
7 purchase totals =	$1,018.92		$1,100.8438	$1,100.85	$1,100.80	$1,100.80