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	$178.58	4.185%	$186.0536	$186.05	$186.05	$186.10
Purchase #2	$238.51	8.663%	$259.1721	$259.17	$259.15	$259.20
Purchase #3	$222.91	7.122%	$238.7857	$238.79	$238.80	$238.80
Purchase #4	$48.76	9.290%	$53.2898	$53.29	$53.30	$53.30
Purchase #5	$54.88	9.128%	$59.8894	$59.89	$59.90	$59.90
Purchase #6	$84.54	11.836%	$94.5462	$94.55	$94.55	$94.50
Purchase #7	$112.60	11.335%	$125.3632	$125.36	$125.35	$125.40
7 purchase totals =	$940.78		$1,017.1000	$1,017.10	$1,017.10	$1,017.20