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	$173.28	3.832%	$179.9201	$179.92	$179.90	$179.90
Purchase #2	$122.96	4.828%	$128.8965	$128.90	$128.90	$128.90
Purchase #3	$200.48	5.106%	$210.7165	$210.72	$210.70	$210.70
Purchase #4	$245.31	5.709%	$259.3147	$259.31	$259.30	$259.30
Purchase #5	$112.52	13.104%	$127.2646	$127.26	$127.25	$127.30
Purchase #6	$177.29	6.306%	$188.4699	$188.47	$188.45	$188.50
Purchase #7	$27.37	3.631%	$28.3638	$28.36	$28.35	$28.40
7 purchase totals =	$1,059.21		$1,122.9461	$1,122.94	$1,122.85	$1,123.00