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	$204.88	5.373%	$215.8882	$215.89	$215.90	$215.90
Purchase #2	$109.56	12.486%	$123.2397	$123.24	$123.25	$123.20
Purchase #3	$197.41	12.607%	$222.2975	$222.30	$222.30	$222.30
Purchase #4	$231.73	9.729%	$254.275	$254.28	$254.30	$254.30
Purchase #5	$76.64	6.788%	$81.8423	$81.84	$81.85	$81.80
Purchase #6	$55.44	7.376%	$59.5293	$59.53	$59.55	$59.50
Purchase #7	$215.74	11.677%	$240.932	$240.93	$240.95	$240.90
7 purchase totals =	$1,091.40		$1,198.0040	$1,198.01	$1,198.10	$1,197.90