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	$198.94	6.223%	$211.32	$211.32	$211.30	$211.30
Purchase #2	$82.30	5.395%	$86.7401	$86.74	$86.75	$86.70
Purchase #3	$10.71	3.692%	$11.1054	$11.11	$11.10	$11.10
Purchase #4	$185.44	8.345%	$200.915	$200.92	$200.90	$200.90
Purchase #5	$129.96	9.582%	$142.4128	$142.41	$142.40	$142.40
Purchase #6	$79.81	12.280%	$89.6107	$89.61	$89.60	$89.60
Purchase #7	$65.29	9.572%	$71.5396	$71.54	$71.55	$71.50
7 purchase totals =	$752.45		$813.6436	$813.65	$813.60	$813.50