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	$180.53	8.588%	$196.0339	$196.03	$196.05	$196.00
Purchase #2	$145.44	9.423%	$159.1448	$159.14	$159.15	$159.10
Purchase #3	$162.50	13.860%	$185.0225	$185.02	$185.00	$185.00
Purchase #4	$231.50	10.865%	$256.6525	$256.65	$256.65	$256.70
Purchase #5	$19.86	7.782%	$21.4055	$21.41	$21.40	$21.40
Purchase #6	$29.69	6.185%	$31.5263	$31.53	$31.55	$31.50
Purchase #7	$207.65	7.498%	$223.2196	$223.22	$223.20	$223.20
7 purchase totals =	$977.17		$1,073.0051	$1,073.00	$1,073.00	$1,072.90