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	$43.73	7.623%	$47.0635	$47.06	$47.05	$47.10
Purchase #2	$169.96	10.651%	$188.0624	$188.06	$188.05	$188.10
Purchase #3	$236.36	12.705%	$266.3895	$266.39	$266.40	$266.40
Purchase #4	$105.25	7.839%	$113.5005	$113.50	$113.50	$113.50
Purchase #5	$196.64	9.226%	$214.782	$214.78	$214.80	$214.80
Purchase #6	$200.98	4.676%	$210.3778	$210.38	$210.40	$210.40
Purchase #7	$67.95	4.824%	$71.2279	$71.23	$71.25	$71.20
7 purchase totals =	$1,020.87		$1,111.4036	$1,111.40	$1,111.45	$1,111.50