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	$242.61	12.625%	$273.2395	$273.24	$273.25	$273.20
Purchase #2	$230.95	3.503%	$239.0402	$239.04	$239.05	$239.00
Purchase #3	$38.71	11.582%	$43.1934	$43.19	$43.20	$43.20
Purchase #4	$233.28	4.342%	$243.409	$243.41	$243.40	$243.40
Purchase #5	$169.35	3.400%	$175.1079	$175.11	$175.10	$175.10
Purchase #6	$47.73	10.478%	$52.7311	$52.73	$52.75	$52.70
Purchase #7	$91.82	9.608%	$100.6421	$100.64	$100.65	$100.60
7 purchase totals =	$1,054.45		$1,127.3632	$1,127.36	$1,127.40	$1,127.20