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	$162.40	5.655%	$171.5837	$171.58	$171.60	$171.60
Purchase #2	$45.49	6.846%	$48.6042	$48.60	$48.60	$48.60
Purchase #3	$43.73	11.114%	$48.5902	$48.59	$48.60	$48.60
Purchase #4	$82.56	4.791%	$86.5154	$86.52	$86.50	$86.50
Purchase #5	$234.76	12.261%	$263.5439	$263.54	$263.55	$263.50
Purchase #6	$245.53	11.696%	$274.2472	$274.25	$274.25	$274.20
Purchase #7	$243.61	10.448%	$269.0624	$269.06	$269.05	$269.10
7 purchase totals =	$1,058.08		$1,162.1470	$1,162.14	$1,162.15	$1,162.10