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	$134.90	11.499%	$150.4122	$150.41	$150.40	$150.40
Purchase #2	$19.38	11.278%	$21.5657	$21.57	$21.55	$21.60
Purchase #3	$207.55	6.708%	$221.4725	$221.47	$221.45	$221.50
Purchase #4	$187.69	4.127%	$195.436	$195.44	$195.45	$195.40
Purchase #5	$246.45	11.533%	$274.8731	$274.87	$274.85	$274.90
Purchase #6	$86.96	4.815%	$91.1471	$91.15	$91.15	$91.10
Purchase #7	$88.93	12.364%	$99.9253	$99.93	$99.95	$99.90
7 purchase totals =	$971.86		$1,054.8319	$1,054.84	$1,054.80	$1,054.80