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	$58.98	13.639%	$67.0243	$67.02	$67.00	$67.00
Purchase #2	$99.31	12.131%	$111.3573	$111.36	$111.35	$111.40
Purchase #3	$106.88	7.525%	$114.9227	$114.92	$114.90	$114.90
Purchase #4	$89.39	11.458%	$99.6323	$99.63	$99.65	$99.60
Purchase #5	$52.91	4.458%	$55.2687	$55.27	$55.25	$55.30
Purchase #6	$215.90	12.699%	$243.3171	$243.32	$243.30	$243.30
Purchase #7	$39.82	10.161%	$43.8661	$43.87	$43.85	$43.90
7 purchase totals =	$663.19		$735.3885	$735.39	$735.30	$735.40