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	$229.83	3.768%	$238.49	$238.49	$238.50	$238.50
Purchase #2	$76.45	3.860%	$79.401	$79.40	$79.40	$79.40
Purchase #3	$38.88	7.864%	$41.9375	$41.94	$41.95	$41.90
Purchase #4	$162.77	10.133%	$179.2635	$179.26	$179.25	$179.30
Purchase #5	$21.52	12.767%	$24.2675	$24.27	$24.25	$24.30
Purchase #6	$223.63	9.709%	$245.3422	$245.34	$245.35	$245.30
Purchase #7	$195.43	5.712%	$206.593	$206.59	$206.60	$206.60
7 purchase totals =	$948.51		$1,015.2947	$1,015.29	$1,015.30	$1,015.30