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	$227.96	3.116%	$235.0632	$235.06	$235.05	$235.10
Purchase #2	$234.44	10.592%	$259.2719	$259.27	$259.25	$259.30
Purchase #3	$69.86	3.600%	$72.375	$72.38	$72.40	$72.40
Purchase #4	$169.59	9.369%	$185.4789	$185.48	$185.50	$185.50
Purchase #5	$170.78	10.741%	$189.1235	$189.12	$189.10	$189.10
Purchase #6	$7.81	9.355%	$8.5406	$8.54	$8.55	$8.50
Purchase #7	$67.26	4.864%	$70.5315	$70.53	$70.55	$70.50
7 purchase totals =	$947.70		$1,020.3846	$1,020.38	$1,020.40	$1,020.40