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	$177.64	10.424%	$196.1572	$196.16	$196.15	$196.20
Purchase #2	$78.63	8.498%	$85.312	$85.31	$85.30	$85.30
Purchase #3	$122.51	7.310%	$131.4655	$131.47	$131.45	$131.50
Purchase #4	$130.92	8.679%	$142.2825	$142.28	$142.30	$142.30
Purchase #5	$201.81	13.544%	$229.1431	$229.14	$229.15	$229.10
Purchase #6	$85.25	12.731%	$96.1032	$96.10	$96.10	$96.10
Purchase #7	$114.82	6.565%	$122.3579	$122.36	$122.35	$122.40
7 purchase totals =	$911.58		$1,002.8214	$1,002.82	$1,002.80	$1,002.90