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	$173.92	13.144%	$196.78	$196.78	$196.80	$196.80
Purchase #2	$29.76	8.841%	$32.3911	$32.39	$32.40	$32.40
Purchase #3	$243.72	10.288%	$268.7939	$268.79	$268.80	$268.80
Purchase #4	$208.68	4.665%	$218.4149	$218.41	$218.40	$218.40
Purchase #5	$178.70	6.435%	$190.1993	$190.20	$190.20	$190.20
Purchase #6	$123.79	4.360%	$129.1872	$129.19	$129.20	$129.20
Purchase #7	$172.30	11.373%	$191.8957	$191.90	$191.90	$191.90
7 purchase totals =	$1,130.87		$1,227.6621	$1,227.66	$1,227.70	$1,227.70