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	$238.38	8.285%	$258.1298	$258.13	$258.15	$258.10
Purchase #2	$224.84	10.687%	$248.8687	$248.87	$248.85	$248.90
Purchase #3	$89.61	8.142%	$96.906	$96.91	$96.90	$96.90
Purchase #4	$201.61	4.295%	$210.2691	$210.27	$210.25	$210.30
Purchase #5	$56.78	4.380%	$59.267	$59.27	$59.25	$59.30
Purchase #6	$97.61	6.676%	$104.1264	$104.13	$104.15	$104.10
Purchase #7	$152.91	6.257%	$162.4776	$162.48	$162.50	$162.50
7 purchase totals =	$1,061.74		$1,140.0446	$1,140.06	$1,140.05	$1,140.10