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	$48.32	9.545%	$52.9321	$52.93	$52.95	$52.90
Purchase #2	$68.36	5.850%	$72.3591	$72.36	$72.35	$72.40
Purchase #3	$89.76	11.272%	$99.8777	$99.88	$99.90	$99.90
Purchase #4	$234.31	4.858%	$245.6928	$245.69	$245.70	$245.70
Purchase #5	$87.71	4.550%	$91.7008	$91.70	$91.70	$91.70
Purchase #6	$232.41	6.484%	$247.4795	$247.48	$247.50	$247.50
Purchase #7	$238.53	12.416%	$268.1459	$268.15	$268.15	$268.10
7 purchase totals =	$999.40		$1,078.1879	$1,078.19	$1,078.25	$1,078.20