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	$73.81	5.836%	$78.1176	$78.12	$78.10	$78.10
Purchase #2	$204.38	8.769%	$222.3021	$222.30	$222.30	$222.30
Purchase #3	$159.63	13.728%	$181.544	$181.54	$181.55	$181.50
Purchase #4	$36.35	13.555%	$41.2772	$41.28	$41.30	$41.30
Purchase #5	$232.87	13.824%	$265.0619	$265.06	$265.05	$265.10
Purchase #6	$63.90	11.834%	$71.4619	$71.46	$71.45	$71.50
Purchase #7	$139.51	6.328%	$148.3382	$148.34	$148.35	$148.30
7 purchase totals =	$910.45		$1,008.1029	$1,008.10	$1,008.10	$1,008.10