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	$220.79	10.279%	$243.485	$243.49	$243.50	$243.50
Purchase #2	$74.60	10.223%	$82.2264	$82.23	$82.25	$82.20
Purchase #3	$163.90	10.471%	$181.062	$181.06	$181.05	$181.10
Purchase #4	$57.43	13.728%	$65.314	$65.31	$65.30	$65.30
Purchase #5	$180.52	8.769%	$196.3498	$196.35	$196.35	$196.30
Purchase #6	$227.37	3.616%	$235.5917	$235.59	$235.60	$235.60
Purchase #7	$231.74	7.841%	$249.9107	$249.91	$249.90	$249.90
7 purchase totals =	$1,156.35		$1,253.9396	$1,253.94	$1,253.95	$1,253.90